TW202240126A - Enhanced hybrid systems and methods for characterizing stress in chemically strengthened transparent substrates - Google Patents

Abstract

The hybrid measurement system [20] includes an evanescent prism coupling spectroscopy (EPCS) sub-system [100] and a light-scattering polarimetry (LSP) sub-system [200]. The EPCS sub-system includes an EPCS light source system [110] optically coupled to an EPCS detector system [140] through an EPCS coupling prism [42A]. The LSP sub-system includes an LSP light source [112] optically coupled to an optical compensator [230], which in turn is optically coupled to a LSP detector system [240] via a LSP coupling prism [42B]. A support structure [46] supports the EPCS and LSP coupling prisms to define a coupling prism assembly [40], which supports the two prisms at a measurement location [ML]. Stress measurements made using the EPCS and LSP sub-systems are combined to fully characterize the stress properties of a transparent chemically strengthened substrate [10]. Methods of processing the EPCS and LSP measurements and enhanced configurations of the EPCS and LSP sub-systems to improve measurement accuracy are also disclosed.

Description

Intensive Hybrid System and Method for Characterizing Stress in Chemically Enhanced Transparent Substrates

This application claims the benefit of priority to U.S. Provisional Application No. 63/152,021, filed February 22, 2021, the contents of which are relied upon and incorporated herein by reference in its entirety.

The present disclosure relates to characterizing stress in transparent chemically amplified substrates, and in particular, to enhanced mixing systems and methods for characterizing stress in chemically amplified transparent substrates.

Transparent substrates that have undergone a chemical strengthening process exhibit increased resistance to scratching and cracking. These substrates are extremely useful for a variety of display applications ranging from television screens to computer screens to mobile handheld device screens to wrist watches. An exemplary chemically enhanced process is an ion-exchange (IOX) process by which ions in the near-surface region of the glass-based substrate are exchanged with foreign ions, eg, from a salt bath.

Fabrication of transparent chemically strengthened (CS) substrates requires characterization of their stress properties to ensure that CS substrates have the desired level of chemical strengthening for a given application. Characterization usually requires measuring the stress profile of the CS substrate from the surface to the center, and related stress parameters, such as surface compressive stress, inflection point stress, peak layer depth, total layer depth, compression depth, and center tension. Other stress-related parameters include changes in birefringence with depth into the CS substrate.

There are two main methods used to characterize the stress of transparent CS substrates. The first uses evanescent prism coupling spectroscopy (EPCS). The EPCS method uses coupling plates to couple light into guided modes supported by, for example, near-surface waveguides (NSWGs) formed in substrates by IOX processes. Coupling beams are also used to couple light out of the NSWG to form a guided mode spectrum. The guided mode spectrum includes: a transverse electric (TE) mode spectrum with TE mode lines; and a transverse magnetic (TM) spectrum with TM mode lines. The TE mode lines and TM mode lines are analyzed to extract stress-related properties including stress profiles. The EPCS method is particularly useful for characterizing stresses in the near-surface region of CS substrates (eg, surface compressive stress and peak layer depth), but not for characterizing central tension CT and depth of compression DOC residing deeper within the substrate.

The second major method utilizes light-scattering polarimetry (LSP). In LSP, the CS substrate is illuminated with input laser light passing through a coupled laser beam at a relatively small angle. Using an optical compensator to continuously change the polarization of the laser light between different polarization states. Scattered light is detected by an image sensor. The stress in the CS substrate causes an optical delay along the optical path, and the amount of stress is proportional to the derivative of the optical delay. The amount of optical retardation can be determined from the detected scattered light intensity distribution, which varies due to constructive and destructive interference for different effective path lengths of the detected light. The LSP method is useful for measuring certain stress-related properties such as central tension (CT) and depth of compression (DOC), but not useful for measuring near-surface stress-related properties.

At present, in order to fully characterize the stress profile of the CS substrate from the surface to the center, the CS substrate is first measured with the EPCS measurement system, then moved to the LSP measurement system, and the two measurement results are stitched together. This is time consuming and introduces a risk of breakage since the CS substrate has to be handled when it is moved between the two metrology systems.

Therefore, it would be advantageous to have a single measurement system capable of performing intensive EPCS and LSP measurements.

The hybrid measurement system and method disclosed in this paper realize the comprehensive stress characterization of the transparent CS substrate, which includes the surface stress S(0), the near-surface compressive stress profile S(x) including the inflection point stress S _k = S(x _k ), Layer depth DOL, central tension CT and compression depth DOC. Global stress characterization is obtained by combining stress calculations using both EPCS and LSP measurements.

An embodiment of the present disclosure relates to a system for characterizing stress in a CS substrate having a top surface and a near-surface waveguide. The system comprises: an EPCS subsystem comprising an EPCS light source system and an EPCS detector system in optical communication via an EPCS coupling plate having an EPCS coupling surface; an LSP subsystem comprising The system comprises an LSP light source system, an optical compensator and an LSP detector system, the LSP detector system is in optical communication with the optical compensator via an LSP coupling plate having an LSP coupling surface; a coupling plate The coupling assembly includes a support frame configured to operably support the EPCS coupling surface and the LSP coupling surface such that the EPCS coupling surface and the LSP coupling surface residing substantially in a common plane; and a support plenum having a surface and a measurement hole, the support plenum configured to support the CS substrate at a measurement hole at the measurement hole and the coupling assembly is operably supported at the measurement hole such that the EPCS coupling surface and the LSP coupling surface substantially reside in the measurement plane. In an example, the EPC subsystem and/or the LSP subsystem have an enhanced configuration as described below.

Another embodiment of the present disclosure relates to a method of measuring a first stress characteristic and a second stress characteristic of a CS substrate having a surface and a near-surface waveguide, the method comprising: the CS substrate of the The surface is operably positioned in a measurement position relative to a coupling interface assembly comprising an EPCS coupling interface and an LSP coupling interface defining adjacent EPCS coupling interfaces and LSP coupling interfaces, respectively. performing an EPCS measurement of the CS substrate using the EPCS coupling interface to obtain the first stress characteristics and performing an LSP measurement of the CS substrate using the LSP coupling interface to obtain the second stress characteristics without from The measurement location removes either the coupling assembly or the CS substrate; and combining the first stress characteristics and the second stress characteristics to create a global stress characterization of the CS substrate. In an example, an EPC subsystem and/or an LSP subsystem having an enhanced configuration as described below may be used to perform an enhanced method of measuring a first stress characteristic and a second stress characteristic.

Another embodiment of the present disclosure relates to an EPCS system for characterizing stress in a CS substrate having a surface and a near-surface waveguide, the EPCS system comprising: a) An EPCS light source system, the EPCS light source system includes: i) an EPCS light source emitting a multi-wavelength EPCS light beam; ii) an optical filter assembly configured to sequentially filter the multi-wavelength EPCS beam to form a series of filtered EPCS beams having different wavelengths; iii) a light guide assembly that transmits the series of filtered EPCS beams as guide light to a focusing optics configured to receive the transmitted filtered EPCS beams and is guided by This forms a series of filtered and focused EPCS beams; b) an EPCS coupling plate forming an EPCS coupling surface with the surface of the CS substrate and receiving the series of filtered and focused EPCS beams and coupling them to the near into and out of the surface waveguide to form a series of filtered and reflected EPCS beams, the series of filtered and reflected EPCS beams each comprising a pair of corresponding filtered and reflected EPCS beams of the near-surface waveguide The pattern spectrum of ; and c) An EPCS detector system comprising: i) a switchable polarization filter operatively connected to a polarization controller to sequentially perform the transverse magnetic (TM) and transverse electrical polarization of the series of filtered and reflected EPCS beams. (transverse electric, TE) polarization filtering to form TM and TE filtered and reflected EPCS beams, the TM and TE filtered and reflected EPCS beams comprising the TM and TE mode spectra of the near-surface waveguide, respectively; and ii) an EPCS digital detector configured to sequentially detect the series of TM and TE filtered and reflected EPCS beams to sequentially capture the near surface waveguide at different filter wavelengths TM and TE images of the corresponding TM and TE mode spectra below.

Another embodiment of the present disclosure relates to the EPCS system described above and herein, wherein the optical filter assembly includes an optical filter wheel.

Another embodiment of the present disclosure relates to the EPCS system as described above and disclosed herein, wherein the optical filter wheel comprises a plurality of optical filter assemblies each comprising an optical filter and a correction member configured to provide focus correction at a given filter wavelength.

Another embodiment of the present disclosure relates to the EPCS system as described above and disclosed herein, wherein the EPCS light source comprises at least one broadband light source element.

Another embodiment of the present disclosure relates to the EPCS system as described above and disclosed herein, wherein the EPCS light source comprises a plurality of light source elements, and the light source elements respectively emit different EPCS light beams with different wavelengths simultaneously or sequentially.

Another embodiment of the present disclosure relates to an EPCS system as described above and disclosed herein, wherein the EPCS beams of different wavelengths are combined to travel along a common axis using one or more photoselective elements to Form multi-wavelength EPCS beams.

Another embodiment of the present disclosure relates to an EPCS system as described above and disclosed herein, wherein the one or more photoselective elements comprise one or more dichroic mirrors.

Another embodiment of the present disclosure relates to the EPCS system as described above and disclosed herein, further comprising a plurality of corrective lenses operably positioned relative to a plurality of light source elements respectively to facilitate optical beam alignment coupled into the input end of the light guide.

Another embodiment of the present disclosure relates to the EPCS system as described above and disclosed herein, further comprising a light diffuser disposed adjacent to the input end of the light guide.

Another embodiment of the present disclosure relates to the EPCS system as described above and disclosed herein, wherein the light guide is liquid filled.

Another embodiment of the present disclosure relates to an EPCS system as described above and disclosed herein, wherein the CS substrate comprises glass material, glass-ceramic material, or crystalline material, and wherein the near-surface waveguide of the CS substrate is formed by a near-surface A peak area and a deep area are defined.

Another embodiment of the present disclosure relates to the EPCS system as described above and disclosed herein, wherein the light guide assembly comprises a light guide having an output end, the EPCS detector system comprises an entrance pupil, and wherein the The output end of the light guide is imaged onto this entrance pupil by focusing optics.

Another embodiment of the present disclosure relates to a hybrid system for characterizing stress in a CS substrate having a top surface and a near-surface waveguide, the hybrid system comprising as described above and disclosed herein EPCS system: a scattered light polarimetry (scattered light polarimetry, LSP) subsystem, the LSP subsystem includes an LSP light source system, an optical compensator and an LSP detector system, the LSP detector system passes through a an LSP coupling plate of an LSP coupling surface in optical communication with the optical compensator; a coupling plate assembly comprising a plate support frame configured to operably support the EPCS coupling surface and the LSP coupling surface such that the EPCS coupling surface and the LSP coupling surface reside substantially in a common plane; and a support plenum having a surface and a measurement hole, The support plenum is configured to support the CS substrate at a measurement plane at the measurement hole, and to operably support the coupling plate assembly at the measurement hole such that the EPCS coupling surface and The LSP coupling surface resides substantially in the measurement plane.

Another embodiment of the present disclosure relates to an EPCS system as described above and disclosed herein for characterizing stress in a CS substrate having a surface and a near-surface waveguide, the EPCS system comprising: a) An EPCS light source system, the EPCS light source system includes: i) an EPCS light source emitting a multi-wavelength EPCS light beam; ii) an optical filter assembly configured to sequentially filter the multi-wavelength EPCS beam to form a series of filtered EPCS beams having different filter wavelengths; iii) a light guide assembly configured to deliver the series of filtered EPCS beams as guide light to a focusing optics configured to receive the transmitted filtered EPCS beams EPCS beams and thereby form a series of filtered and focused EPCS beams; b) an EPCS coupling plate forming an EPCS coupling surface with the surface of the CS substrate and receiving the focused sequentially filtered EPCS beam and coupling it out of the EPCS coupling surface at the EPCS coupling surface a near-surface waveguide to form a reflected and sequentially filtered EPCS beam comprising at least first and second modes of the near-surface waveguide for at least first and second filter wavelengths spectrum; and c) An EPCS detector system comprising: i) at least one switchable polarizing filter configured to sequentially perform transverse magnetic (TM) and transverse electrical (TM) of the reflected and sequentially filtered EPCS beam. electric, TE) polarization filtering to form at least first and second TM- and TE-reflected and sequentially-filtered EPCS beams, the at least first and second TM- and TE-reflected and sequentially-filtered EPCS beams, respectively comprising first and second TM and TE mode spectra of the near-surface waveguide at the at least first and second wavelengths; and ii) at least first and second EPCS digital detectors configured to detect the at least first and second TM and TE reflected, respectively, and in accordance with sequentially filtered EPCS beam to capture respective at least first and second TM and TE images of the first and TM and TE mode spectra of the near-surface waveguide.

Another embodiment of the present disclosure relates to an EPCS system as described above and disclosed herein, wherein the at least first and second EPCS digital detectors are along respective at least first and second detector axes resident, and wherein the at least one switchable polarizing filter comprises a sensor respectively disposed along the at least first and second detector axes and upstream of a corresponding one of the first and second EPCS digital detectors At least first and second switchable polarizing filters.

Another embodiment of the present disclosure relates to an EPCS system as described above and disclosed herein, wherein the CS substrate comprises glass material, glass-ceramic material, or crystalline material, and wherein the near-surface waveguide of the CS substrate is formed by a near-surface A peak area and a deep area are defined.

Another embodiment of the present disclosure relates to the EPCS system as described above and disclosed herein, wherein the light guide assembly comprises a light guide having an output end, the EPCS detector system comprises an entrance pupil, and wherein the The output end of the light guide is imaged onto this entrance pupil.

An embodiment of the present disclosure relates to a system for characterizing stress in a CS substrate having a top surface and a near-surface waveguide, the system comprising: the EPCS described above and disclosed herein System; a scattered light polarimetry (scattered light polarimetry, LSP) subsystem, the LSP subsystem includes an LSP light source system, an optical compensator and an LSP detector system, the LSP detector system passes through a The LSP coupling plate of the LSP coupling surface is in optical communication with the optical compensator; a coupling plate assembly including a plate support frame configured to operatively support the optical compensator the EPCS coupling surface and the LSP coupling surface such that the EPCS coupling surface and the LSP coupling surface reside substantially in a common plane; and a support plenum having a surface and a measurement hole, the The support plenum is configured to support the CS substrate at a measurement plane at the measurement hole, and to operably support the coupling plate assembly at the measurement hole such that the EPCS coupling surface and the The LSP coupling surface substantially resides in this measurement plane.

Another embodiment of the present disclosure relates to an EPCS system as described above and disclosed herein for characterizing stress in a CS substrate having a surface and a near-surface waveguide, the EPCS system comprising: a) An EPCS light source system, the EPCS light source system includes: i) an EPCS light source emitting a multi-wavelength EPCS light beam comprising a plurality of wavelengths; ii) a light guide assembly that transmits the multi-wavelength EPCS beam from the EPCS light source to a focusing optics configured to receive the multi-wavelength EPCS beam and form a focused multi-wavelength EPCS beam; b) an EPCS coupling plate that forms an EPCS coupling surface with the surface of the CS substrate and receives the multi-wavelength EPCS beam and couples it into the near-surface waveguide and couples it at the EPCS coupling surface exiting the near-surface waveguide to form a reflected multi-wavelength EPCS beam comprising a mode spectrum corresponding to a plurality of wavelengths of the near-surface waveguide for the multi-wavelength EPCS beam; and c) An EPCS detector system comprising: i) a switchable polarization filter operably positioned to receive the reflected multi-wavelength EPCS beam and in turn form a transverse magnetic polarized (TM) multi-wavelength EPCS beam and a transverse electric polarized (TE) multi-wavelength EPCS light beam. ii) an optical filter assembly operatively positioned to sequentially filter the TM and the TE multi-wavelength EPCS beams at two or more filter wavelengths to form two or two or more sequentially filtered TM and TE EPCS beams comprising, respectively, TM and TE at the two or more filter wavelengths mode spectrum; iii) an EPCS digital detector configured to sequentially detect the sequentially filtered TM and TE EPCS beams to sequentially capture the near surface waveguide at the two or both TM and TE images of the corresponding TM and TE mode spectra at more than one filter wavelength.

Another embodiment of the present disclosure relates to an EPCS system as described above and disclosed herein, wherein the CS substrate comprises glass material, glass-ceramic material, or crystalline material, and wherein the near-surface waveguide of the CS substrate is formed by a near-surface A peak area and a deep area are defined.

Another embodiment of the present disclosure relates to the EPCS system as described above and disclosed herein, wherein the light guide assembly comprises a light guide having an output end, the EPCS detector system comprises an entrance pupil, and wherein the The output end of the light guide is imaged onto this entrance pupil by focusing optics.

An embodiment of the present disclosure relates to a system for characterizing stress in a CS substrate having a top surface and a near-surface waveguide, the system comprising: an EPCS system as described above and disclosed herein ; a scattered light polarimetry (scattered light polarimetry, LSP) subsystem, the LSP subsystem includes a LSP light source system, an optical compensator and a LSP detector system, the LSP detector system through a LSP with a an LSP coupling plate of a coupling surface in optical communication with the optical compensator; a coupling plate assembly including a plate support frame configured to operably support the EPCS coupling the inflatable and the LSP coupling in such that the EPCS coupling surface and the LSP coupling surface generally reside in a common plane; and a support inflatable having a surface and a measurement hole, the support The plenum is configured to support the CS substrate at a measurement plane at the measurement hole, and to operably support the coupling plate assembly at the measurement hole such that the EPCS coupling surface and the LSP The coupling surface substantially resides in this measurement plane.

Another embodiment of the present disclosure relates to a method of performing evanescent coupling spectroscopy to characterize stress in a CS substrate having a surface and a near-surface waveguide, the method comprising: a) forming a multi-wavelength EPCS beam having multiple wavelengths; b) sequentially filtering the EPCS multi-wavelength beam to form a series of filtered EPCS beams, the series of filtered EPCS beams each having a different wavelength of one of the plurality of wavelengths; c) transmitting the series of EPCS filtered beams through a light guide to a focusing optics to form a series of focused EPCS filtered beams; d) directing the series of focused filtered EPCS beams to an EPCS coupling plate which forms an EPCS coupling surface with the surface of the CS substrate and which receives the series of filtered EPCS beams and at the coupling it into and out of the near-surface waveguide at the EPCS coupling surface to form a series of reflected and filtered EPCS beams comprising the near-surface waveguide respectively at a mode spectrum at one of the plurality of wavelengths; e) sequentially polarizing each of the reflected and filtered EPCS beams to form a transverse magnetic (TM) filtered and reflected EPCS beam for each reflected and filtered EPCS beam and a transverse electric (TE) filtered and reflected EPCS beam; and f) sequentially digitally detecting the TM-filtered and reflected EPCS beam and the TE-filtered and reflected EPCS beam to sequentially capture the corresponding TM and TE mode spectra of the near-surface waveguide for different multiple wavelengths TM and TE images.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, and further comprising: processing sequentially captured TM and TE images of corresponding TM and TE mode spectra to characterize at least one stress of the CS substrate relevant nature.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, wherein the sequential filtering includes passing the multi-wavelength light beam through an optical filter assembly supported by a filter wheel.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, wherein each optical filter assembly includes an optical filter and a correction member configured to correct for wavelength dependence focus error.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, wherein the sequentially polarizing comprises: passing the reflected and filtered EPCS beams through a magnetic polarizing crystal, the polarizing crystal Operably connected to a polarization controller.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, wherein the CS substrate comprises glass material, glass-ceramic material, or crystalline material, and wherein the near-surface waveguide of the CS substrate is formed by a near-surface spike zone and a deep zone are defined.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, wherein the sequential digital detection of the TM and TE filtered and reflected EPCS beams uses a single EPCS digital detector to execute.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, wherein the sequential digital detection of the TM and TE filtered and reflected EPCS beams uses a plurality of EPCS digital detectors To perform, the EPCS digital detectors are spatially separated using dichroic mirrors.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, wherein the light guide has an output, the series of reflected filtered EPCS light beams are received and processed by an EPCS detector system , the EPCS detector system has an entrance pupil, and wherein the output end of the light guide is imaged onto the entrance pupil by a focusing optical system.

Another embodiment of the present disclosure relates to a light-scattering polarimetry (LSP) system for characterizing stress in a CS substrate having a body, a surface, and a surface formed on the body. In vivo near-surface waveguide, the LSP system consists of: a) an LSP light source system comprising in sequence along a first system axis: i) a laser diode emitting an LSP beam having a power of at least 1 microwatt and centered on a wavelength of 405 nm; ii) a shutter system configured to periodically block the LSP beam; iii) a rotatable half-wave plate; iv) a first fixed polarizer; v) a first focusing lens; vi) a light diffuser; vii) a second focusing lens b) an optical compensator disposed downstream of the LPS light source and configured to impart a time-varying polarization to the LSP beam, the optical compensator comprising in sequence along the system axis: i) a polarizing beam splitter configured to receive the LSP beam from the LSP light source and transmit a first portion of the LSP beam along the first system axis and direct the LSP along a spectrometer axis a second part of the light beam; ii) a spectrometer arranged along the spectrometer axis and configured to receive and spectroscopically process the second portion of the LSP light beam; iii) a second fixed polarizer; iv) a variable polarizer that imparts the time-varying polarization to the LSP beam to form a time-varyingly polarized LSP beam; c) an axially movable focusing lens disposed downstream of the optical compensator and configured to receive and focus the time-varyingly polarized LSP beam to form a focused time-varyingly polarized LSP beam; d) an LSP coupling interface that interfaces with the surface of the CS substrate to form an LSP coupling interface, wherein the focused time-varyingly polarized LSP beam is focused at the LSP coupling interface to extract from the CS substrate Stress-inducing features within the body generate scattered light; e) an LSP detector system disposed downstream of the LSP coupling plate and configured to receive the scattered light, the LSP detector system comprising: i) an LSP digital detector; and ii) a collection optics system that collects the scattered light and directs it to the LSP digital detector to form an LSP image at the digital detector.

Another embodiment of the present disclosure relates to the LSP system as described above and disclosed herein, wherein the variable polarizer comprises a liquid crystal variable retarder (LCVR), the LCVR operable to Connect to a polarizer controller.

Another embodiment of the present disclosure relates to the LSP system as described above and disclosed herein, wherein the LCVR is in operative communication with a temperature controller that maintains the LCVR in a selected temperature range Inside.

Another embodiment of the present disclosure relates to the LSP system as described above and disclosed herein, wherein the selected temperature range is between 35°C and 40°C.

Another embodiment of the present disclosure relates to the LSP system as described above and disclosed herein, wherein the axially movable focusing lens comprises a lens element supported by a lens support and wherein the lens support is mechanically attached connected to a linear motor.

Another embodiment of the present disclosure relates to the LSP system as described above and disclosed herein, wherein the LSP beam has a power of at least 10 microwatts.

Another embodiment of the present disclosure relates to the LSP system as described above and disclosed herein, wherein the LSP beam has a power of at least 50 microwatts.

An embodiment of the present disclosure relates to a system for characterizing stress in a CS substrate having a top surface and a near-surface waveguide, the system comprising: LSP as described above and disclosed herein an evanescent prism coupling spectroscopy (EPCS) subsystem comprising an EPCS light source system and an EPCS detector in optical communication via an EPCS coupling prism having an EPCS coupling surface a coupling system; a coupling system assembly comprising a system support frame configured to operably support the EPCS coupling system and the LSP coupling system such that the the EPCS coupling surface and the LSP coupling surface reside substantially in a common plane; and a support plenum having a surface and a measurement hole configured to support the CS substrate on A measurement plane at the measurement hole, and the coupling assembly is operably supported at the measurement hole such that the EPCS coupling surface and the LSP coupling surface reside substantially in the measurement plane.

Another embodiment of the present disclosure is a method of performing light scattering polarimetry (LSP) to characterize stress in a CS substrate having a body, a surface, and a near-surface waveguide, the near-surface waveguide A surface waveguide forming a stress-dependent feature in the body, the method comprising: generating a light beam from a laser diode having an output power of at least 1 microwatt and a central wavelength of 405 nm; the light beam A first portion of the beam is directed to a spectrometer to measure the wavelength of the beam and the amount of power in the beam; a second portion of the beam is imparted using a temperature-controlled liquid crystal variable retarder (LCVR) a time-varying polarization to form a time-varyingly polarized light beam; focusing the time-varyingly polarized light beam onto a coupling surface formed by a coupling plate interfacing with the surface of the CS substrate for receiving from the main The stress-related features in the body create scattered light; and directing the scattered light to a digital detector to capture an LSP image at the digital detector.

Another embodiment of the present disclosure relates to the method as described above and as disclosed herein, wherein the body of the CS substrate is made of glass material.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, further comprising: maintaining the LCVR at a temperature in the range of 35°C to 40°C.

Another embodiment of the present disclosure relates to the method as described above and as disclosed herein, wherein the time-varyingly polarized beam follows a beam path through the body of the CS substrate, and further comprises by A beam center of the beam is estimated by performing a sloped Gaussian fit to the scattered light for a selected depth along the beam path into the body of the CS substrate to define a first set of beam centers; and passing through the The first set of beam centers are fitted to a first line to define a first fitted line.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, further comprising estimating a center point of the time-varyingly polarized light beam by combining a second line to define a second fitted line; and identifying the center point at which the first fitted line and the second fitted line intersect.

Another embodiment of the present disclosure relates to the method as described above and as disclosed herein, wherein the time-varyingly polarized beam follows a beam path through the body of the CS substrate, and further comprises by Determine an entry point of the time-varyingly polarized light beam into the CS substrate by identifying an edge intensity profile of the LSP image along one of the first fitted line and the second fitted line, wherein the edge Intensity transitions from a maximum value I _MAX to a minimum value I _MIN representing a background intensity value; and determining a half maximum intensity value I _1/2 intermediate between the maximum intensity value I _MAX and the minimum intensity value I _MIN and defining The entry point is at the half maximum intensity value I _1/2 .

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, wherein the LSP beam has a power of at least 10 microwatts.

Another embodiment of the present disclosure relates to the method as described above and disclosed herein, wherein the LSP light beam has a power of at least 50 microwatts.

Additional features and advantages will be set forth in the following detailed description, and in part will be apparent to those skilled in the art from this description or by practice as illustrated in the written description and claims thereof and the accompanying drawings Examples are recognized. It is to be understood that both the foregoing general description and the following detailed description are exemplary only, and are intended to provide an overview or framework for understanding the nature and character of what is claimed.

Reference will now be made in detail to various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same or similar reference numbers and symbols will be used throughout the drawings to refer to the same or like parts. The drawings are not necessarily drawn to scale, and those skilled in the art will recognize where the drawings have been simplified to show key aspects of the disclosure.

The claims as set forth below are incorporated into and constitute a part of this detailed description.

For reference, Cartesian coordinates are shown in some of the Figures, and Cartesian coordinates are not intended to limit direction or orientation.

In some parts of the discussion the z-coordinate is used for the depth direction into the substrate, while in other parts of the discussion different coordinates are used.

The abbreviation "IOX" stands for "ion exchanged" or "ion exchanged", depending on the context of the discussion.

The abbreviation "CS" means "chemically amplified" when used to describe the type of substrate (as in "CS substrate"). The abbreviation CS can also mean "compressive stress" and which meaning is used for this abbreviation will be apparent from the context of the discussion.

The term "reinforced" for CS substrates considered herein means that the original CS substrate has undergone certain processes to create some stress profile that may have various shapes, generally intended to make the CS substrate stronger and thus more difficult to crack. Exemplary enhancement processes include ion exchange, tempering, annealing, and similar thermal processes.

The term "transparent" as used in relation to a CS substrate means a CS substrate having sufficient optical transmission at a given measurement wavelength (i.e., EPCS wavelength λ _A or LSP wavelength λ _B ) to perform satisfactorily on the CS substrate. measurements (ie, EPCS measurements or LSP measurements) that yield sufficiently accurate measurements of the stress characteristics associated with a given measurement.

The abbreviation "ms" stands for "milliseconds".

The abbreviation "nm" stands for "nanometer".

The term "near-surface", such as when referring to a near-surface waveguide or a near-surface spike region of a CS substrate, refers to the portion of the substrate body that resides in close proximity to a given surface (eg, top or measurement surface) of the CS substrate.

In an example, a glass-based substrate is used to form the CS substrate. As used herein, the term "glass-based substrate" includes any substrate made in whole or in part of glass, such as laminates of glass and non-glass materials, laminates of glass and crystalline materials, and glass ceramics (including amorphous and crystalline phases). object. Thus, in an example, a glass-based CS substrate may consist entirely of a glass material, while in another example may consist entirely of a glass-ceramic material.

The terms "image" and "line image" are used herein to describe the light distribution ( That is, the intensity distribution), and an imaging system is not necessary to form an LSP image as contemplated herein.

In the discussion below, the LSP subsystem is configured to cycle between two or more states of polarization (or just simply "polarization"). In an example, there may be up to eight different polarization states per cycle, combining linear, elliptical, and circular polarizations, as known in the art.

The term "stress" as used herein may generally mean compressive stress or tensile stress. In the graphs of Figures 15B, 16B, 19B, and 19D, compressive stress is negative and tensile stress is positive. Whether the stress is compressive or tensile depends on the location or depth region of the CS substrate considered. Positive values of compressive stress are understood to mean the magnitude of the compressive stress. Stress is denoted by S or by σ, and is taken to refer to compressive stress unless otherwise indicated or understood from the context of the discussion. In some cases, compressive stress is denoted as CS, such as for the inflection point stress CS _k . The stress profile is the stress S as a function of depth into the CS substrate, and the depth coordinates can be any local coordinates, and both z and x are used as local coordinates in the discussion below.

In an example, "characterization" of a CS substrate includes determining one or more stress-based properties of the CS substrate, such as stress profile S(z), depth of layer DOL, surface stress S(0), depth of compression DOC, central tension CT and the birefringence profile B(z). In the example, the characterization utilizes both EPCS and LSP measurements, which provide first and second stress characteristics, respectively, which when combined provide a "comprehensive characterization of the stress characteristics of the CS substrate". ”, wherein the term “full characterization” means that the characterization of stress and stress-related properties is more complete than would be possible with only the first stress characteristic measured by EPCS or only the second stress characteristic measured by LSP.

The abbreviation "OR" stands for "optical retardation" and is measured in units of radians ("Radians") unless otherwise noted. The graph of optical retardation versus depth into the CS substrate is hereinafter referred to as an "OR versus D" graph or graph, where D is understood as the depth into the body of the CS substrate from the top (measuring) surface.

The term "index matching fluid" means a fluid that has substantially the same refractive index as another material to facilitate optical coupling. In an example, the index matching fluid comprises an oil or a mixture of oils. The refractive index of the index matching fluid is denoted by n _f or n _oil , ie these two expressions are used interchangeably hereinafter.

The terms "plate" and "wave plate" are used interchangeably when referring to a type of wave plate (eg, a half-wave plate is the same as a half-wave plate, etc.). To avoid confusion, the term "wave plate" is hereinafter referred to as "plate" when the term in progress includes the word "wave".

The term "subsystem" is used where convenient to distinguish it from larger systems in which smaller systems reside. Accordingly, for ease of discussion, the terms "system" and "subsystem" are used interchangeably.

CS Substrate

FIG. 1A is a top view of an exemplary type of CS substrate 10 in the form of a planar sheet. The CS substrate 10 has a main body 11 , a top surface 12 , a bottom surface 14 and side surfaces 16 . The CS substrate 10 has a thickness TH and a mid-plane MP intermediate and parallel to the top surface 12 and the bottom surface 14 .

In some cases, the thickness TH may be in the range of 0.050 mm ≤ TH ≤ 2 mm, such as 0.20 mm ≤ TH ≤ 2 mm, 0.25 mm ≤ TH ≤ 2 mm, 0.3 mm ≤ TH ≤ 2 mm, or 0.3 mm ≤ TH ≤ 1 mm and any and all subranges formed between such endpoints.

An exemplary type of CS substrate 10 is glass-based and is used as a protective cover for displays and/or housings of mobile devices such as smartphones, tablets, laptops, GPS devices, and the like. Such CS substrates 10 tend to be thin and planar, such as shown in Figure 1A.

The CS substrate 10 includes a near-surface waveguide (NSWG) 18 residing in the body 11 near the top surface 12 . In an example, NSWG 18 is formed using a 10X process and is bounded by at least one 10X region with a varying refractive index.

FIG. 1B is a graph of refractive index n versus depth z into a CS substrate for an exemplary NSWG 18 . The surface refractive index is denoted n _s , while the bulk refractive index (ie, the refractive index of the substrate material that has not been affected by the chemical enhancement process) is denoted n _B .

The graph of FIG. 1B shows an exemplary refractive index profile n(z) that defines two (10×) regions, namely, a first near-surface peak region R1 and a second deep region R2. There is also a third region R3 deeper than the second deep region and referred to herein as the "bulk" region, which has a refractive index _nB . The near-surface peak region R1 has a maximum refractive index n _s at the surface and the refractive index decreases rapidly with depth (z) over a relatively small depth z = D1 up to a value n _k , where the depth z = D1 defines the first "Spike" layer depth DOL _sp . The deep region R2 has a slower decrease in refractive index from _nk up to a depth D2 which defines the total layer depth DOL _T , where the third integral region R3 begins. The first region R1 and the second region R2 intersect (and thus define) an inflection point KN located at z = z _{k where} , as described above, the refractive index n = _nk and z = z _k is associated with the inflection point (compressive) stress CS _k .

Due to the two distinct refractive index regions R1 and R2 in NSWG 18, some guided modes propagate only in the uppermost spike region R1, while other guided modes travel in both regions R1 and R2, while others The guided mode only travels in the deep region R2. Other refractive index profiles n(z) include a more uniform variation of the refractive index. Some of the deep guided modes may extend into the overall region R3.

The refractive index profile n(z) of FIG. 1B can be formed by a dual IOX (DIOX) process, where one IOX process forms the deep region R2 and another IOX process different from the first IOX process forms the peak region R1. The graph of FIG. 1B represents a DIOX process performed in a Li-containing glass CS substrate 10 in which Li ions are exchanged with potassium and sodium ions in two distinct 10X processes, wherein the potassium 10X process produces a peak region R1.

mix EPCS-LSP system

FIG. 2A is a schematic diagram of a hybrid EPCS-LSP metrology system (“hybrid system”) 20 as disclosed herein, shown with an exemplary CS substrate 10 . The hybrid system 20 includes a coupling assembly 40 , an EPCS measurement subsystem (“EPCS subsystem”) 100 , an LSP measurement subsystem (“LSP subsystem”) 200 and a system controller 400 . The coupling assembly 40 defines the measurement location ML on the CS substrate 10 .

The EPCS subsystem 100 generates an EPCS measurement signal SA representing a first stress characteristic of the CS substrate at the measurement location ML, as embodied in the mode spectrum of the guided mode of the NSWG 18 . The first stress characteristic may include one or more of the following: surface compressive stress S(0), total layer depth DOL _T , peak layer depth DOL _sp , inflection point stress CS _k and birefringence B.

The LSP subsystem 200 generates the LSP measurement signal SB, which represents the second stress characteristic of the CS substrate at the measurement location ML, as embodied in the optical retardation (OR) information, which enters the CS substrate according to ( The depth including the deep region R2) varies. The second stress characteristic may include one or more of: stress profile, depth of compression DOC, and central tension CT.

In an example, the EPCS and LSP measurements of the first and second stress characteristics are performed without moving the measurement location ML. In another example, the EPCS and LSP measurements of the first and second stress characteristics are performed by: translating the coupled slab assembly 40 such that the EPCS and LSP measurements are performed at the same location on the substrate, Rather than at slightly spaced locations at the measurement locations as defined by the configuration of the coupling assembly.

In an example, the EPCS and LSP measurements of the first and second stress characteristics are performed without removing the coupling pad assembly 40 or the CS substrate 10 from the measurement location ML. This represents an advantage over prior art in that both EPCS and LSP measurements can be made in a single system without having to remove or otherwise process the CS substrate to bring it to a different measurement system.

The EPCS measurement signal SA and the LSP measurement signal SB are sent to the system controller 400 for processing. The system controller 400 may include, for example, a microcontroller, a computer, a programmable logic controller (programmable logic controller, PLC) and the like. In an example, the system controller 400 is configured with instructions (e.g., software) embodied in a non-transitory computer-readable medium to control the operation of the hybrid system 20 and execute the SB to determine the calculation of the first and second stress characteristics of the CS substrate 10 .

In an example, the system controller 400 processes the EPCS measurement signal SA and the LSP measurement signal SB to define the stress profile and related stress characteristics from the top surface 12 of the CS substrate 10 at least up to the bottom of the deep region R2. In other words, the system controller combines the first and second stress characteristics obtained from the EPCS subsystem 100 and the LSP subsystem 200 to produce a larger CS substrate than would be possible with only one of the metrology subsystems. A more complete or "comprehensive" stress profile.

Coupler assembly 40 includes an EPCS coupler 42A and an LSP coupler 42B operably supported by a coupler support structure 46 . The coupling assembly 40 is operatively disposed on or near the top surface 12 of the CS substrate 10 . In the examples discussed below, the EPCS coupling panel 42A and the LSP coupling panel 42B may be separate coupling panels or different sections of a single (common) coupling panel.

With continued reference to FIG. 2A , hybrid system 20 includes an exemplary housing 21 having dimensions L1 and L2. For a relatively compact embodiment of the hybrid system 20, exemplary dimensions of L1 and L2 are in the range of 8 inches to 12 inches.

The EPCS subsystem 100 includes an EPCS light source system 110 and an EPCS detector system 140 optically coupled via an EPCS coupling port 42A. The LSP subsystem 200 includes an LSP light source system 210, an optical compensator 230, and an LSP detector system 240 optically coupled to the optical compensator via an LSP coupling port 42B. EPCS detector system 140 and LSP detector system 240 are operatively connected to system controller 400 . Examples of EPCS subsystem 100 are described in US Patent No. 9,534,981 and US Patent No. 9,696,207, which are incorporated herein by reference. Examples of LSP subsystem 200 are described in US Patent No. 4,655,589 and US Provisional Patent Application Serial No. 62/753,388, which patent and application are incorporated herein by reference.

FIG. 2B is a more detailed schematic diagram of the hybrid EPCS-LSP system of FIG. 2A showing an exemplary configuration of the EPCS subsystem 100 and the LSP subsystem 200 . FIG. 3A is a schematic diagram of an exemplary EPCS subsystem 100 . 4A-4C are schematic diagrams of an exemplary LSP subsystem 200 .

EPCS subsystem

Referring to FIGS. 2B and 3A , the EPCS light source system 110 of the EPCS subsystem 100 includes an EPCS light source 112 that generates an EPCS light beam 116 at a first wavelength λ _A along a first axis A1 . The first wavelength λ _A may also be referred to as an EPCS wavelength.

The EPCS light source system 110 also includes, along the first axis A1 , an optical polarizer 118 , a light diffuser 122 residing downstream of the EPCS light source 112 , and a focusing lens 120 residing downstream of the light diffuser. In an example, the light source comprises a light-emitting diode (LED), and further in an example, the LED operates at an EPCS measurement wavelength λ _A of 365 nm. The EPCS detector system 140 resides along the second axis A2 and includes, in order along the second axis: focusing lens 142, bandpass filter 144 centered at wavelength λ _A , attenuator 146, TM-TE polarizer 148 (which has TM and TE segments (not shown)) and a digital detector (e.g., digital camera, image sensor, CCD array, etc.) Defined TM and TE segments (not shown).

EPCS beam 116 from EPCS light source 112 is diffused by light diffuser 122 and focused by focusing lens 120 to form focused EPCS beam 116F. Focused EPCS beam 116F is incident on EPCS coupling beam 42A at input surface 43A. This couples the focused EPCS beam into the NSWG 18 at the first (EPCS) coupling interface INT1, which is formed by the top surface 12 of the CS substrate and the bottom or "coupling" of the EPCS coupling interface 42A. Surface 45A defines. The first coupling interface INT1 may include an index matching fluid 5A, as discussed in more detail below.

Reflected EPCS beam 116R is formed by focused EPCS beam 116F at first EPCS coupling interface INT1 and exits output surface 44A of EPCS coupling interface 42A to travel along second axis A2. The first axis A1 and the second axis A2 reside in a common plane (eg, the x-z plane of FIG. 3A ). The reflected EPCS beam 116R includes information about the mode spectrum of the NSWG 18 guided mode. Reflected EPCS beam 116R is focused by focusing lens 142 in EPCS detector system 140 to form an image of the mode spectrum of the guided light at EPCS digital detector 150 .

Bandpass filter 144 ensures that only reflected EPCS beam 116R reaches EPCS digit detector 150 . The attenuator 146 ensures that the reflected EPCS beam 116R has a proper intensity distribution for efficient digit detection. The TM-TE polarizer 148 defines the TM and TE sections of the digital detector so that the EPCS digital detector 150 can capture the TM and TE mode spectrum. The TM and TE mode spectra are embodied in the first detector signal SA, which is sent to the system controller 400 for processing. It should be noted that the order of bandpass filter 144, attenuator 146, and focusing lens 142 is not critical and is intentionally shown to be different between Figures 2B and 3A to illustrate this.

FIG. 3B is a schematic representation of the idealized pattern spectrum 160 as captured by the EPCS digital detector 150 . Show local (x,y) Cartesian coordinates for easy reference. The mode spectrum 160 has a TM total-internal-reflection (TIR) section 161TM and a TE TIR section 161TE associated with the TM and TE guided modes, respectively, and a TM and TE radiation mode and a leakage mode, respectively. Linked non-TIR segment 162TM and non-TIR segment 162TE. TIR segment 161TM includes one or more TM "stripes" or TM mode lines 163TM, and TIR segment 161 TE includes one or more TE "stripes" or TE mode lines 163TE. The TM mode lines 163TM and TE mode lines 163TE are generally aligned in the x-direction and spaced apart in the y-direction.

The transition regions ("transitions") 166TM and 166TE between the TIR segments 161TM, 161TE and the non-TIR segments 162TM, 162TE define the critical angles for optical coupling of TM and TE polarized light into and out of the NSWG 18 of the CS substrate 10, and is called the critical angle transition. The difference in location of the onset of critical angle transitions 166TM and _166TE is proportional to the inflection point stress CSk, and this ratio is indicated by " ~ _CSk " in Figure 3B.

According to the configuration of the EPCS subsystem 100 , the TM mode line 163TM and the TE mode line 163TE can be open lines or dark lines. In FIG. 3B , for convenience of illustration, the TM mode line 163TM and the TE mode line 163TE are shown as dark lines.

The stress characteristics for EPCS measurements are calculated based on the difference in y-positions of the TM mode line 163TM and the TE mode line 163TE in the mode spectrum 160 . Birefringence B is the difference between the effective refractive index of TM polarized light and TE polarized light, where the effective refractive index is represented by the y position of the mode line. The surface compressive stress S(0) = CS is calculated from the y distance between the model lines (effective refractive index) and the ratio B/SOC, where SOC is the stress optics coefficient. At least two TM mode lines 163TM and TE mode lines 163TE are needed to calculate the surface stress S(0). Additional model lines are required to calculate the compressive stress profile S(z). Layer depth DOL _T is a measure of the stress penetration or ion penetration length into the body 11 of the CS substrate 10, and in the case of 1OX process, can also be calculated from the y-position and number of the mode lines 163TM and 163TE. The TM and TE mode lines along the y-axis are thus the most fundamental measurements for inferring the stress-dependent properties of the CS substrate 10 . Calculations for determining the stress characteristics of the CS substrate 10 based on EPCS measurements made using the EPCS subsystem 100 are performed in the system controller 400 .

LSP subsystem

Referring now to FIGS. 2B and 4A-4C, the LSP light source system 210 of the LSP subsystem 200 includes an LSP light source 212 that generates an LSP light beam 216 having a wavelength _λB along a third axis A3. In an example, LSP light source 212 is configured as a laser diode operating at a second wavelength λ _B = 415 nm. The second wavelength λ _B may also be referred to as an LSP wavelength.

The LSP light source system 210 includes, in order along the third axis A3: an optional neutral density filter 218 (shown in FIGS. 2B and 4A ), a first focusing lens 220, a movable light diffuser 222, and the second focusing lens 224 . The movable light diffuser 222 may comprise a holographic element configured to perform light diffusion at wavelength _λΒ . In examples, the movable light diffuser may comprise a rotating light diffuser or an oscillating light diffuser. One or more folding mirrors FM can be used to fold the LSP subsystem 200 to make it more compact.

The optical compensator 230 resides along the third (folded) axis A3 and comprises a polarizer which may be in the form of a polarizing beam splitter PBS 232 . The optical compensator 230 also includes a half-wave plate 234H and a third-wave plate 234Q, wherein one of the wave plates can be rotated relative to the other to change the polarization state of the LSP beam 216 . In an example, the optical compensator 230 may comprise an electronically controlled polarizing modulator, such as a liquid crystal based modulator or a ferroelectric liquid crystal based modulator or similar modulator.

In an example, optical compensator 230 is operably connected to or otherwise includes a controller (not shown) that controls the polarization switching operations performed by the optical compensator. In an example, optical compensator 230 may include a single liquid crystal device. In another example, the optical compensator 230 may include multiple elements, such as polarizers, wave plates, filters, filters (eg, wedge-shaped filters), and the like. In an example, optical compensator 230 causes LSP beam 216 to cycle through the full polarization (ie, change between two or more selected polarizations) anywhere from less than 1 second to 10 seconds. In an example, optical compensator 230 may be operably connected to and controlled by system controller 400 .

A third focusing lens 236 resides downstream of the optical compensator 230 and is used to form the focused LSP beam 216F that is directed to the LSP coupling lens 42B. The LSP coupling pad has respective input and output surfaces 43B, 44B and a bottom or "coupling" surface 45B. Coupling surface 45B and top surface 12 of CS substrate 10 define a second (LSP) coupling interface IF2. In the example the second coupling interface INT2 comprises a refractive index matching fluid 5B, as discussed below.

The LSP detector system 240 resides along a fourth axis A4, which is orthogonal to the third axis A3, ie, the fourth axis A4 resides in the Y-Z plane.

In an example, LSP detector system 240 includes collection optics 243 and digital detector (eg, CCD camera) 246 . In an example, collection optics 243 are telecentric and have a magnification of one. The LSP detector system 240 may also include a bandpass filter 244 centered at the second wavelength [lambda] _B . In the example shown in FIG. 4C, digital detector 246 includes an array of imaging pixels 247, which in an example may have dimensions between 1.8 microns and 10 microns.

In operation of the LSP subsystem 200, the focused LSP beam 216F is incident on the input surface 43B of the LSP coupling plate 42B and travels to the coupling surface 45B, then passes through the index matching fluid 5B and reaches the top of the CS substrate 10 surface 12 to enter the main body 11 of the CS substrate. Focused LSP beam 216F has the selected polarization as defined by optical compensator 230 at any given time. The input focused LSP beam 216F (polarized) is scattered by the stress-inducing features in the body 11 of the CS substrate 10 to form a scattered LSP beam 216S. Scattered LSP beam 216S exits CS substrate 10 at top surface 12, returns through second coupling interface INT2, and exits LSP coupling interface 42B at output surface 44B. Scattered LSP beam 216S travels to LSP detector system 240 and is directed by collection optics 243 to digital detector 246 . Scattered LSP beam 216S forms LSP image 248 on digital detector 246, as shown in the close-up view in FIG. 4D. This defines the digital LSP image. LSP image 248, as discussed below, is considered a digital LSP image unless otherwise indicated. The characteristic "X" shape of the LSP image 248 is known in the LSP art and is due to the reflection of the scattered LSP beam 216S from various interfaces associated with the LSP interface INT2, such as the CS substrate 10, the LSP coupling interface 42B, and the refractive index Match Fluid 5B as defined.

As shown in FIG. 4D, the X shape of LSP image 248 is defined by two intersecting line images LI each having a local length coordinate _XL along its length. Each line image LI has an intensity distribution I(X _{L )} , which is measured by the pixels 247 coincident with the line image. The digital detector converts the intensity distribution I(X _L ) into a second detector signal SB which is sent to the system controller 400 . Only one of the line images LI is needed to perform the measurement. In an example, image processing is used to identify a portion of LSP image 248 for subsequent processing to extract optical delay information, as explained below.

In an embodiment, a given measurement of the CS substrate 10 using the LSP subsystem 200 includes taking the measurement within a measurement time t _M of between 1 second and 10 seconds. During measurement time _tM , the polarization state of LSP beam 216 changes between different polarization states, preferably performing one or more cycles through the polarization states. Simultaneously, for each polarization state, digital detector 246 captures LSP image 248 during exposure time _tE . In an example, the exposure time t _E is about the same as the frame rate FR of the digital detector 246 . An exemplary exposure time tE ₌ 50 ms, which corresponds to a frame rate FR = 20 frames/second. The exposure time t _E can also be shorter than the frame rate.

The electronically captured LSP image 248 differs in its intensity distribution I(X _L ) depending on the polarization state of the input focused LSP beam 216F and the optical delay induced along the beam path. The difference is due to the difference in destructive and constructive interference between different polarization states along the length of the scattered LSP beam 216S, which is a function of the depth D into the CS substrate 10 . The difference between the multiple intensity distributions I(X _L ) for different polarization states is used by the system controller 400 to calculate the optical retardation OR, which depends on entering the body 11 of the CS substrate 10 , using relationships well known in the art. The depth D varies. Likewise, multiple optical retardation curves OR and D ("OR and D curves") are calculated using the difference in intensity distribution I(X _L ). For example, for a measurement time t _M of 3 seconds and 20 frames/ With an image sensor frame rate FR of 2 seconds, a total of 60 I(X _L ) vs. D graphs can be generated to calculate OR and D and use them to calculate one or more stress-related properties of the CS substrate 10 .

Although the intensity distribution I(X _L ) of the LSP image 248 necessarily differs between the polarization states of the input beam 112, when stress exists in the CS substrate 10, different OR and D curves calculated from the measured intensity distribution (graph) The process should ideally be the same for a given CS substrate at a given measurement position of the CS substrate, where the stress profile is (ideally) constant.

Although the LSP metrology technique can produce the stress profile S(z), it generally does not produce an accurate representation of the stress profile in the near-surface region of the CS substrate 10 . There are at least two problematic effects that challenge the use of LSP measurements from LSP subsystem 200 to extract an accurate characterization of the near-surface stress profile of CS substrate 10 . One problematic effect is known as the "fireball" effect, which is caused by excessive light scattering at the LSP interface INT2. Excess light scattering creates noise that corrupts the LSP measurement data in the near surface region, which in the example is the first 60 microns to 100 microns below the top surface 12 of the CS substrate 10 .

Another problematic effect is caused by the convolution of photons scattered from different depths into the signal corresponding to a particular depth. This convolution alters the signal significantly in regions of rapidly changing stress, often in the near-surface compression region, most often in the first 80, 100 or 150 microns, but sometimes as high as 200 microns. The rapid change zone is thicker for Li-based glass of greater thickness)

Some prior art LSP systems attempt to reduce these convolution effects by using a very focused beam close to the CS substrate surface, where the beam diameter is as small as 10 microns. Unfortunately, this causes other problems, such as increased laser noise (eg, speckle) in the region of interest at the same depth, making the extracted stress profile in the near-surface region even less reliable.

Coupling assembly

The hybrid system 20 utilizes the aforesaid coupler assembly 40, which operably supports the EPCS coupler 42A and the LSP coupler 42B for the EPCS subsystem 100 and The LSP sub-system 200 provides the coupling.

FIG. 5A is a top view of a top portion of an example coupling assembly 40 showing an example support frame 48 . FIG. 5B is similar to FIG. 5A and additionally includes a top view of cover plate 60 . Exemplary support frame 48 includes EPCS frame section 48A supporting EPCS coupling frame 42A and LSP frame section 48B supporting LSP coupling frame 42B. Support frame 48 also includes isolation member 50 disposed between EPCS frame section 48A and LSP frame section 48B, configured to optically isolate EPCS coupling frame 42A and LSP coupling frame 42B. In an example, isolation member 50 also prevents mixing of index matching fluids 5A and 5B used with EPCS-coupling 42A and LSP-coupling 42B, respectively. In another example, isolation member 50 allows a single index matching fluid to be used with both the EPCS coupling 42A and the LSP coupling 42B, i.e., a single index matching fluid can be defined between two different Flow between the first interface INT1 and the second interface INT2. In one example, the isolation member 50 is separate from and attached to the support frame 48 . In another example, the spacer member 50 is part of the support frame 48, ie, is integrally formed with the support frame during its formation.

In an example, the EPCS and LSP frame sections 48B and spacer members 50 include fastening tabs 52 that include mounting holes 53 that allow the cover plate 60 to be fastened using fastening members (not shown). Fastened to frame section. Cover plate 60 includes a first aperture 62A sized to accommodate coupling surface 45A of EPCS coupling interface 42A, and a second aperture 62B sized to accommodate coupling surface 45B of LSP coupling interface 42B.

Figures 6A and 6B illustrate an exemplary method in which the EPCS frame section 48A and the LSP frame section 48B are formed using a resin molding process. This process provides precise alignment of EPCS coupled 42A and LSP coupled 42B. In an example, the molding process is performed with the exemplary EPCS coupling plate 42A and LSP coupling plate 42B in place on the stable platform 75 . This process is discussed in more detail below.

FIG. 7 is an x-z cross-sectional view of an exemplary bracing support structure 46 attached to a hybrid using fastening tabs 52 and fastening members 54 (such as screws) passing through mounting holes 53. Exemplary support plenum 70 of system 20 . The support plenum 70 has a top surface 71 and a measurement hole 72 . Top surface 71 defines an exemplary measurement plane MP at measurement aperture 72 . The support structure 46 is supported by the support plenum 70 such that the EPCS coupled plenum 42A and the LSP coupled plenum 42B reside at the measurement hole 72 . In an example, EPCS coupling surface 45A of EPCS coupling surface 42A and LSP coupling surface 45B of LSP coupling surface 42B reside or substantially reside at measurement plane MP.

In an example, the CS substrate 10 is operably supported by a movable substrate holder 80 that holds the CS substrate over the metrology aperture 72 such that the EPCS coupling 42A and the LSP coupling 42B The top surface 12 of the CS substrate 10 may be interfaced to establish a first coupling interface INT1 and a second coupling interface INT2 located or substantially located at the measurement plane MP. In an example, the movable substrate holder 80 is transported over the top surface 71 of the support plenum 70 using transport elements 73 such as rollers, wheels, slides, bearings, and the like. In an example, the CS substrate 10 is supported by the movable substrate holder 80 at an inner lip 82 that supports an outer (peripheral) portion of the top surface 12 of the CS substrate. In an example, the plane of the inner lip 82 defines an exemplary measurement plane MP. Fig. 7 therefore shows two different exemplary positions of the measurement plane MP.

FIG. 8A shows a top view of an example in which a support plenum 70 is in the form of a plate comprising pressure-vacuum (PV) elements or PV pipes 90 (e.g., PV rods) for Pneumatically engage the CS substrate 10 to pull the CS substrate via vacuum (negative pressure) onto the coupling surface 45A of the EPCS coupling surface 42A and onto the coupling surface 45B of the LSP coupling surface 42B and then from the surface via pressure (positive pressure). Release the CS substrate. FIG. 8B is a cross-sectional view of the support plenum and measurement hole of FIG. 8A showing an exemplary vacuum system 91 including a PV element (PV rod) 90 and a vacuum source 92 .

Note that the inner lip 82 of the movable substrate holder 80 defines a stop member for limiting the vertical movement of the CS substrate 10 when vacuum is applied to the CS substrate via the vacuum system 91 .

Hybrid system using a single index-matching fluid

An exemplary embodiment of a hybrid system 20 such as that shown in FIG. 6D employs a single index matching fluid 5 having a refractive index n _f for both the EPCS subsystem 100 and the LSP subsystem 200 . This is a counter-intuitive approach, since a single index matching fluid 5 would generally be considered incapable of producing good metrology results for both subsystems simultaneously for at least the following reasons.

If the index matching fluid is selected based on EPCS metrology considerations, the index matching fluid has a refractive index _nf that is substantially higher (eg, 0.1 or more higher) than the surface refractive index _ns of the CS substrate to facilitate optical coupling into guided mode and obtained good fringe contrast in the captured TM and TE mode spectra.

On the other hand, this level of refractive index contrast (difference) Δn between the refractive index matching fluid 5 and the refractive index of the top surface 12 of the CS substrate 10 causes significant surface scattering at the coupling interface INT2 due to the surface Beam deflection under refractive index mismatch associated with microroughness. This is problematic for accurate extraction of retardation and stress measurements at intermediate depths based on receiving and processing scattered light from the CS substrate. High surface scattering produces a "fireball" on the image of the scattered beam, eg, a large spot where the pixels 247 of the digital detector (CCD camera) 246 are filled with photons. This results in the loss of a large amount of stress-related information. A well-polished or pristine surface, such as formed by fusion drawing, tends to have less scattering.

If the refractive index matching fluid _nf is approximately matched (e.g., similar to, slightly higher than, or slightly lower than) the surface refractive index _nS of the CS substrate 10 to ensure low surface scattering, then when near the surface (e.g., such as The fringe contrast in the mode spectrum 160 is often poor in the presence of sharp changes in the refractive index in the peak region R1 (see FIG. 1B ) (caused by shallow concentrated spikes in the K2O concentration as produced by the 10X process ₎ . Furthermore, the position and contrast of TM stripes 163TM and TE stripes 163TE become dependent on the thickness of the index matching fluid. These two effects make it difficult to accurately measure surface CS and peak DOL using the EPCS subsystem 100 .

If the index matching fluid 5 is chosen to have a refractive index _nf lower than the substrate (bulk) refractive _index nB of the CS substrate 10 (which is often also meant to be lower than the surface index), the thickness of the index matching fluid must Small (eg, less than 0.4 microns) to enable optical coupling into the waveguide mode of the near-surface portion of the NSWG 18 (peak region R1 ) for surface CS measurements. Measuring the critical angle of coupled light traveling in the deep region R2 between the surface peak region R1 and the bulk region R3 also requires a small thickness. This is difficult to achieve consistently in a production environment due to the problem of small particle contamination. These issues pose problems for accurately measuring the surface (compressive) stress S(0) and the "inflection point stress" _Sk at the bottom of the surface index peak region R1 for double IOX Li-containing glasses and glass-ceramics.

As a result, a single index matching fluid 5 for both EPCS and LSP measurements can be used under selected conditions where the peak region R1 of the CS substrate 10 has a normalized slope S _n = |(λ/n)dn (z)/dz| < 0.0005, or more preferably S _n < 0.0004, where λ is the measurement wavelength and n(z) is the refractive index of the CS substrate 10 at the measurement wavelength.

In one embodiment, the refractive index _nf is higher (larger) than the surface refractive index _ns of the glass of the CS substrate 10 by an amount Δn = _nf − _ns in the range of 0.02 to 0.06. Both EPCS and LSP measurements yield sufficient measurement results. When S _n < 0.0004, it is preferred that Δ n is in the high end of the above range, for example, 0.05 to 0.06.

In one aspect of the present invention, the measurement wavelength λ _A of the EPCS measurement is reduced to reduce the normalization slope S _n so as to more easily meet the above conditions. In one example, the measurement wavelength λ _A of the EPCS measurement is 5% or more shorter than the measurement wavelength λ _B of the LSP measurement to help achieve a smaller normalized slope S _n . In an example, one or more light blocks (not shown) may be selectively positioned on the beam path of the EPCS subsystem 100 to preferentially block light rays propagating at greater angles of incidence, which correspond to greater angles of incidence. High effective refractive index. This improves the contrast of the captured TM and TE fringes of the guided mode of the near-surface spike region R1 of the NSWG 18 .

In another embodiment, the surface peak region R1 may have a normalized slope S _n > 0.0005. In an example, the refractive index matching fluid can be selected to have a refractive _{index nf} at the EPCS measurement wavelength _λB that is very close to the z position at the inflection point KN (i.e., at the bottom of the peak region R1 ) effective refractive index. In this case, n _f ≈ n _crit , where n _crit is the refractive index associated with the critical angle of the peak region (ie, below which light does not travel as a guided wave within the peak region R1 ).

。 In many cases of practical interest, the effective refractive index difference between the TM guided wave and the TE guided wave at the position corresponding to the bottom of the surface peak region R1 is relatively small. For example, in most cases of practical interest the difference is less than 0.0006 refractive-index units (RIU), and most often between 0.00015 RIU and 0.0005 RIU. In the example,

.

及/或 n _oil ≈

。更具體而言， n _f 不會大體上小於TM及TE臨界折射率中之較小者，且亦將不顯著大於TM及TE臨界折射率中之最大者。因此，在實例中(且以數學方式表達上述情況)：

In some instances it is sufficient to state that n _f ≈ n _crit , which means that n _oil ≈

and/or n _oil ≈

. More specifically, _nf will not be substantially less than the smaller of the TM and TE critical indices, and will also not be significantly greater than the largest of the TM and TE critical indices. So, in the instance (and expressing the above mathematically):

中之較大者，但是理想地亦不顯著大於兩個臨界折射率中之較小者。 The upper limit in the equation immediately above is defined to reduce the likelihood of missing the fringe associated with peak region R1 by making _nf greater than the effective index of the fringe when no index matching fluid is present. Therefore, in order to achieve proper consideration of all modes in order to accurately calculate the depth of the surface peak region R1 (which in the example is defined by the potassium IOX process), it is preferred that _nf is not significantly greater than the TM and TE critical indices

The larger of the two critical indices of refraction is ideally not significantly greater than the smaller of the two critical indices of refraction.

或

)之間存在顯著的有效折射率差異時，與尖峰區R1相關聯的TM及TE模式頻譜中的模式條紋在折射率空間中相隔較遠，例如，相隔超過0.0015 RIU，或較佳地相隔超過0.002 RIU，或甚至更佳地相隔超過0.0025 RIU。在此實施例中，折射率匹配流體的折射率可被選擇為更接近兩個臨界折射率中之較高者，且可能高於兩個臨界折射率中之較大者：

或

In one embodiment, when the effective refractive index of the last fringe in a particular polarization state (TM or TE) is different from the corresponding critical refractive index (

or

), the mode fringes in the TM and TE mode spectra associated with the peak region R1 are far apart in refractive index space, e.g., separated by more than 0.0015 RIU, or preferably separated by more than 0.002 RIU, or even better separated by more than 0.0025 RIU. In this embodiment, the refractive index of the index matching fluid may be selected to be closer to, and possibly higher than, the higher of the two critical indices of refraction:

or

These differences in effective refractive index are readily used with the EPCS subsystem 100 by measuring the location of the critical angles (which correspond to the intensity transitions 166TM and 166TE on the sensor from bright total internal reflection to dark (partial reflection)) and and/or the difference in fringe position is established and takes into account the calibration of the instrument (angle per RIU, or pixel per RIU, or point spacing on the sensor plane per RIU).

In another embodiment with more general application, the index n _oil of the index matching fluid is selected to be closer to the lower of the TM and TE effective indices. This enables capture of TM and TE fringes whose effective refractive index may be close to the critical index, but may require a relatively close proximity (e.g., several wavelength).

或

。 More specifically, it is preferred in this embodiment to

or

.

Furthermore, to reduce significant changes in the shape of the critical angle transition, it may be preferable to

或甚至

or even

In some cases of practical interest, the guided mode with the lowest effective index has its effective index very close to the critical index (within about 0.0002 RIU). In this case it may be desirable to also impose stricter requirements on the refractive index of the index matching fluid which would be limited according to the above:

In cases where n _oil is less than at least one of the two critical indices of refraction, obtaining a high-contrast transition for correct measurement of the critical index of refraction n _crit may require EPCS coupling of coupling surface 45A of plate 42A to the top of CS substrate 10 The aforementioned close proximity (eg, a few wavelengths) between surfaces 12 . In an example, this close proximity is achieved by use of a vacuum system that draws the sample toward the pan through PV tubing 90 that is pneumatically connected to a vacuum source 92 .

In another example, when the refractive index n _oil of the index matching fluid is not significantly different from the effective refractive index of the guided optical mode used to calculate the surface compressive stress CS, for the surface compressive stress S(0) = CS Systematic errors in calculations are corrected. In particular, it is best to take advantage of this correction when:

In an exemplary embodiment, the correction is specified by calibrating systematic errors, for example, by comparing the surface compressive stress CS measured using the preferred inventive dual-purpose index-matching fluid with that by using the more known Compared with the CS measured by the index matching fluid of the more known index matching fluid having a relatively large refractive index n _oil , such as the CS used to measure the bulk refractive index n _B in the range of 1.45 to 1.55 The oil of substrate 10 has n _oil = 1.72 at λ _A = 590 nm.

In a related embodiment, the systematic error can also be calibrated for the width of the TM stripe 163TM and the TE stripe 163TE, as this width can be correlated with the index matching fluid and simultaneously with the amount of systematic error in the measurement of the surface compressive stress CS Associated. It should be noted that the systematic error will also depend on the refractive index slope S _n of the refractive index profile of the surface peak region R1 of the CS substrate 10 . This means that systematic errors can be defined for a particular type of CS substrate with a surface index of refraction S _n falling within a relatively narrow range. Such a narrow range is typically for CS substrates employing Li-based glass that has been reinforced using a 10X process.

Hybrid system using two different index matching fluids

An exemplary embodiment of the hybrid system 20 employs two different index matching fluids 5 (denoted 5A and 5B) for the EPCS subsystem 100 and the LSP subsystem 200, respectively, wherein the two different index matching fluids 5A and 5B have The corresponding refractive indices n _fA and n _fB (or n _oil-A and n _oil-B ).

Using two different index matching fluids 5A and 5B requires keeping the two index matching fluids separate so that they do not mix with each other. In one example discussed above in connection with FIGS. 5A and 5B , the EPCS support structure 46 includes a spacer member 50 positioned between the EPCS coupling 42A and the LSP coupling 42B to maintain the two indices of refraction matching. Fluids 5A and 5B are separate, ie fluidly isolated from each other.

In another embodiment, a pressurized gas (e.g., air) is introduced into the small gap between the EPCS coupling panel 42A and the LSP coupling panel 42B to define an "air curtain" 30 (see FIG. 2B ), " Air curtain 30 ensures that index matching fluids 5A and 5B do not interact with each other while CS substrate 10 is being measured in mixing system 20. This separation would then enable simultaneous automatic dripping of respective index matching fluids 5A and 5B onto their respective EPCS-coupled 42A and LSP-coupled 42B, allowing simultaneous measurements. In an example, air curtain 30 may be formed using vacuum system 91 (see FIG. 8B ).

Hybrid systems with reduced crosstalk

Given the proximity of the EPCS coupling 42A and the LSP coupling 42B, crosstalk between the EPCS subsystem 100 and the LSP subsystem 200 may occur. Such crosstalk can reduce the accuracy of stress measurements for each subsystem. The various embodiments described below for reducing (including eliminating) crosstalk may be used alone or in combination.

In one example, the EPCS detector system 140 for the EPCS subsystem 100 includes the aforementioned bandpass filter 144 centered on the EPCS measurement wavelength _λΑ . Meanwhile, the LSP detector system 240 for the LSP subsystem 200 includes the aforementioned bandpass filter 244 centered on the LSP measurement wavelength λ _B. In an example, the respective bandwidths of bandpass filters 144 and 244 are narrow enough to substantially filter out other subsystem measurement wavelengths. Because the bandpass filter can be made very narrow (eg, a few nanometers), only a small difference in measurement wavelength (eg, 10 nm) will be sufficient to use the bandpass filter to reduce or eliminate crosstalk. In an example, a given bandpass filter can be inserted anywhere between the corresponding coupling filter and detector system.

In another embodiment, an optically opaque barrier to the EPCS measurement wavelength λ _A and the LSP measurement wavelength λ _B is disposed between the EPCS coupling panel 42A and the LSP coupling panel 42B. In an example, the barriers are in the form of isolation members 50, as discussed above in connection with FIG. 5A. The isolation member 50 may be formed of a rigid material such as aluminum or a non-rigid material such as rubber as long as it can prevent the EPCS and LSP measurement light from communicating between the EPCS coupling plate and the LSP coupling plate. As noted above, isolation member 50 may also be configured to serve the dual purpose of optical isolation and fluid isolation.

Coupling

The hybrid system 20 provides the most accurate measurements when the EPCS coupling 42A and LSP coupling 42B are aligned relative to each other and their coupling surfaces 45A and 45B reside in a common plane.

In order to achieve this alignment, the coupling fender assembly 40 employs the aforementioned fringe support structure 46 used. In an example of forming the support structure 46, the coupling surface 45A of the EPCS coupling surface 42A and the coupling surface 45B of the LSP coupling surface 42B are first ground and polished to high flatness and perpendicularity. Referring again to FIG. 6A, the EPCS coupling surface 45A and the LSP coupling surface 45B are then placed on a stable platform 75, such as a precisely flat bar of granite, with the coupling surfaces 45A and 45B residing on the surface 76 of the stable platform.

Referring to Figure 6B, mold 49 is mounted at surface 76 on stable platform 75, and resin 49R is then poured into the mold. After the resin has hardened, the walls of the mold 49 are removed to define the bracing support structure 46 that couples the brazing assembly 40, such as shown in FIG. 5B. In an example, the molded wall support structure 46 includes a spacer member 50 in the form of a thin wall 47 between the EPCS coupling wall 42A and the LSP coupling wall 42B, as shown in FIG. 6C. In an example, the molded pleated support structure 46 is formed such that at least one of the pleated shells is partially clad to avoid crosstalk. In an example, the molded plaster support structure 46 comprises or consists of a single molded structure, ie, is a single piece (ie, a single piece) formed from a single material, and thus is not formed by bonding Formed from two or more components.

In an example, the molded pan support structure 46 includes fastening tabs 52 that include mounting holes 53 for securing the pan support structure 46 to the inflatable portion (see also FIG. 5A ). The use of a movable substrate monitor 80 as shown in FIG. 7 and described above enables EPCS and LSP measurements to be taken at the same location on the CS substrate 10 . The measurement positions of the EPCS subsystem 100 and the LSP subsystem 200 can be set by moving the movable substrate monitor 80 under the operation of the system controller 400 using precision linear motors (eg, piezoelectric actuators).

In an example, the coupling support structure 46 includes sections that are movable relative to each other such that the EPCS coupling coupling 42A and the LSP coupling coupling 42B are movable relative to each other (e.g., axial or z-direction, as shown in FIG. 6C ). shown). In an example, the support frame 48 of the support structure includes adjacent walls configured such that one wall can slide relative to the other in a controlled manner. In the example of FIG. 6C, the EPCS coupling plate 42A is shown as having moved in the z-direction relative to the LSP coupling plate 42B.

FIG. 6D is similar to FIG. 4C and shows an embodiment of hybrid system 20 in which EPCS subsystem 100 and LSP subsystem 200 share common coupling interface 42, i.e., common coupling interface 42 serves as EPCS coupling interface 42A and The LSP couples both of 騜鏡42B. A single index matching fluid 5 is also used. The various surfaces of the common coupling surface 42 serve a dual purpose, for example, the coupling surfaces are denoted 45A and 45B because they serve the dual purpose of performing EPCS coupling as well as LSP coupling. In an example, the bandpass filters 144 and 244 of the EPCS subsystem 100 and the LSP subsystem 200 are separated from the bandpass filters 144 and 244 of different wavelengths λ _A and λ _B (e.g., separated by at least the frequency of one of the bandpass filters 144 and 244 in wavelength). wide) to substantially reduce or eliminate crosstalk between subsystems. In the example of the common coupled beam 42, the coupled beam has ECSP segment PS1 and LSP segment PS2, and further in this example, these segments may be separate, i.e., EPCS beam 116 and LSP beam 216 generally Stay in their corresponding segment, except for a small amount of scattered light.

Reduce substrate warpage

The CS substrate 10 may be large enough that it may warp to the extent that making accurate EPCS and LSP stress measurements becomes problematic. In particular, a warped CS substrate 10 can make it difficult to establish the EPCS coupling interface INT1 and the LSP coupling interface INT2 required for EPCS and LSP stress measurements.

Referring again to Figures 8A and 8B, a vacuum system 91 is used to reduce or eliminate substrate warpage. PV pipes (PV rods) 90 are in pneumatic communication with the top surface 12 of the CS substrate 10 through the measurement holes 72 in the support plenum 70, which supports the CS substrate such that the top surface 12 generally resides in the measurement plane MP place. Activation of the vacuum source 92 generates a reduced pressure near the coupling assembly 40 via the PV conduit 90, thereby generating a downward force FD on the CS substrate from the high ambient pressure, as indicated by the two large arrows. The PV conduit 90 enables control of the height of the CS substrate relative to the top surface 71 of the support plenum 70 (and thus relative to the measurement plane MP) to within an accuracy of ±5 microns. The use of the vacuum system 91 also reduces vibration and enables non-contact control of the CS substrate for dynamic handling and inspection without the need to stabilize the CS substrate on the vacuum chuck.

PV pipe 90 is commercially available and can be configured for warping reduction, as shown in Figures 8A and 8B. It may be desirable to omit some of the PV piping 90 proximate to the coupling assembly 40 to avoid interference with the EPCS beam 116 and the LSP beam 216 and the various components of the EPCS subsystem 100 and the LSP subsystem 200 immediately below the support plenum 70 . In an example, one or more stop members 94 may be used to hold the CS substrate 10 in place on the support plenum 70 .

In some cases, it may be desirable for at least one of the EPCS coupling interface 42A and the LSP coupling interface 42B to be adjustable from the other. In such a case, the coupling fender assembly 40 may comprise two separate fringe support structures 46, one or both of which are adjustable. In one example, the EPCS coupling plate 42A can be adjusted in the z-direction to optimize the contrast of the TM and TE mode fringes in the mode spectrum. This can be accomplished by using a single-axis micropositioner attached to the cannon support structure 46, which holds the EPCS-coupled cannon in a movable configuration.

deal with EPCS and LSP Measurement result

FIG. 9 is a schematic diagram of an exemplary user interface 410 displayed by the system controller 400 of the hybrid system 20 . User interface 410 includes EPCS section 412A showing mode spectrum 160 produced by EPCS subsystem 100 and LSP section 412B showing digital LSP image 248D produced by LSP subsystem 200 . The software in the system controller 400 is configured to: use the EPCS measurements from the EPCS subsystem 100 (i.e., the mode spectrum 160 ) to calculate the first stress characteristic of the CS substrate, and use the LSP measurements from the LSP subsystem 200 The result (ie, digital LSP image 248D) calculates a second stress characteristic of the CS substrate, and then combines the measurements to produce a complete or global stress characterization of the CS substrate.

deal with LSP Measurement result

In an example, system controller 400 is configured (eg, configured with software) to process LSP image 248 to extract a “second” or LSP stress characteristic obtained from LSP subsystem 200 . This includes digitally characterizing the contours of the LSP image 248 using Gaussian blur Otsu delimitation performed as part of the contour detection method to facilitate calculation of optical retardation and depth (OR and D).

FIG. 10A is an exemplary representation of LSP image 248 as shown in LSP section 412B of user interface 410 . The detection of the LSP image 248 by the digital detector 246 forms a digital LSP image 248D. The digital LSP image 248D may be referred to as an original LSP image or an original digital LSP image. The LSP section 412B of the user interface also displays a histogram of the scattered light intensity constituting the digital LSP image 248D and some related statistical measurements. In this exemplary view, the primary beam incidence into the CS substrate is from the lower right corner of the cross to the center. From the center of the cross to the upper right corner, the digital camera observes the reflection from the air surface of the CS substrate on the side of the beam (see Figure 11C below), which is due to total internal reflection. From the center of the cross to the lower left corner, the direct beam has been reflected from the CS substrate air surface and travels back through the thickness of the CS substrate towards the LSP coupling plate. From center to upper left, a digital camera observes reflections of reflected beams.

The digital LSP image 248D mainly contains very bright pixels and pixels with little or no exposure. Referring to Figure 10B, as part of the contour detection method, a Gaussian blur is applied to the initial (raw) digital LSP image 248D (left image) to reduce any residual noise. The result is blurred LSP image 248B (right image). Gaussian blur is applied in a manner that does not obscure the optical delay information encoded in the intensity variations of the digital LSP image 248D.

Referring now to FIG. 10C, the Otsu limit is applied to the (Gaussian) blurred LSP image 248B of FIG. 10B to obtain a threshold LSP image 248T. The Otsu bounding mechanism uses the image histogram (see Figure 10A) to select an intensity value below which all pixels are set to zero. The bright regions in Figure 10C represent all pixels with intensities above this threshold.

FIG. 10D shows the next processing step which involves using the threshold LSP image 248T to define the LSP image contour 248C using a binarization method, such as by applying a known open source binarization algorithm, such as available from Open Source code image processing algorithm (eg, via OpenCV). The example uses an image coordinate system with 0.0 in the upper left corner and increasing values in the right (x) and downward (y) directions. The LSP image profile 248C contains an array of points that can be divided into quadrants to find the following five critical points of the cross-shaped image: upper left corner, upper right corner, lower left corner, lower right corner, and center. The close-up of Figure 10D shows an example of the bottom left corner point detection obtained by finding the lowest X value and highest Y value in the area. The same process is repeated for all four corners, and the center is determined by averaging the corner X and Y values.

FIG. 10E shows the final LSP image contour 248C with fully defined contours and processed regions. In the example, the lower right segment of the processed "X" LSP image profile 248C (see trapezoidal area) is then used to calculate LSP stress properties. The horizontal lines in LSP image outline 248C in Figure 10E are at constant depth. The intensity (eg, sum, peak, or average) Gaussian blur across the horizon from each of the images acquired while modulating the polarization of the light source was used as input for subsequent analysis to obtain OR and D data.

Thus, the threshold LSP image 248T and the LSP image profile 248C are used to define a "mask" that identifies a portion or portions of the captured or Gaussian blurred LSP image 248B that will be used to calculate the optical delay OR, The optical retardation OR is a function of the depth (D) into the CS substrate 10, as explained above.

CS Substrate thickness extraction and beam angle calculation

FIG. 11A is a view of the CS substrate 10 . FIG. 11A also shows the beam path of a portion of the focused LSP beam 216F inside the body 11 of the CS substrate 10 after passing through the LSP coupling beam 42B (not shown). FIG. 11B shows a close-up view of the edge portion of the CS substrate 10 as a region of interest for calculating the CS substrate thickness TH. 11C-11E are additional views of the path of the focused LSP beam 216F within the CS substrate. For ease of illustration, LSP-coupled 騜鏡42B is not shown.

By observing the edge of the CS substrate 10 along the propagation direction of the focused LSP beam 216F, the thickness of the CS substrate 10 as seen by the digital detector 246 of the LSP detector system 240 can be highlighted, as shown in FIG. 11B . Since the digital detector 246 is observing the focused LSP beam 216F passing through the angled LSP coupling beam 42B (e.g., at a 45° angle), the thickness TH of the CS substrate 10 can be calculated as TH = x /{ Cos (45°) where x represents the path length in the plane of the digital detector 246 .

Once the thickness TH is calculated, the propagation angle A of the focused LSP beam 216F within the CS substrate (see FIG. 11E ) can be determined by observing the edge of the CS substrate 10 in the direction of the digital detector 246, And use the schematic diagram of Fig. 11E to use the following formula to determine the propagation angle A : A=ArcTan(W/TH) wherein W is the center intersection C of the LSP image contour 248C obtained from the above contour detection method and the lower right corner of the image contour (lower right, LR) the horizontal distance between critical points. Once the processed area is selected, the digital detector 246 records a number of LSP images 248 as a function of the input polarization. The optical delay information as a function of depth into the CS substrate is then extracted using techniques known in the art.

lock detection method

The lock-in detection method is a signal analysis technique that has proven to be very good at quickly extracting signals obscured by noise. For this method to work, the period of the signal must be known.

The measurement (detector) signal SB from the LSP subsystem 200 has a period that depends on the polarization rotation rate of the optical compensator 230 . When rotating half-wave plate 234RH is used in optical compensator 230, one full rotation corresponds to four oscillations of the polarization state of scattered LSP beam 216S.

。 The lock-in method applied to the LSP measurement signal SB = s(t) is derived as follows, where t is time. The LSP measurement signal s(t) is considered to be centered around zero and have a noise amount ("noise factor") N . The measurement data D(t) received by the system controller 400 can be expressed as: D(t) = s(t) + N The measurement signal s(t) can be generalized into the following form s(t) = A cos( ft + φ) where φ is the phase value to be extracted and f is the known frequency of the signal. This signal can be "locked" by multiplying it by a common test wave of equal and negative period (and arbitrary phase) W(t) = cos (-f - θ) to yield the following equation:

.

The first two terms of the immediately above equation for D(t)*W(t) oscillate according to the time variable t . However, the last term is a constant that can be extracted via strong low-pass filtering of the product wave. This is achieved by averaging the product wave, since the average of the wave approximates the wave's offset value over many oscillations.

This approximation causes a slight error if the measured signal s(t) does not have many oscillations (eg, less than one full oscillation) or if the signal has a non-integer number of half periods. This error can be reduced by only taking the signal average over the largest half-cycle of the signal. For example, if the signal has about 3.7 oscillations, take a signal average of at most 3.5 periods.

及相位φ。已知此情況，可將餘弦擬合於此等常數(例如，使用最小平方擬合)，且可提取相位φ。亦可提取信號的振幅 A。 Once low-pass filtering is performed using known means, the product D(t)*W(t) is reduced to a constant term [A/2] cos(- θ + φ) . Recall that φ is the desired phase value and θ is the arbitrary phase of the test wave. Thus, if θ is incremented through a series of numbers, the constant resulting from low-pass filtering of the product wave for each increment will oscillate according to the time-invariant cosine function [ A /2] cos(- θ + φ). This cosine wave has wavenumber -1 , amplitude

and phase φ. Knowing this, cosines can be fitted to these constants (eg, using a least squares fit), and the phase φ can be extracted. The amplitude A of the signal can also be extracted.

The lock-in method for signal extraction has proven to be much faster than conventional sinusoidal fitting. Figure 12A is the average calculation time in milliseconds (ms) required to extract the phase φ of the noisy signal for both the lock-in method (L or black curve) and the sine method (S or gray curve) T and noise factor N. The information in Figure 12A was collected during a series of tests. In these tests, random noise is added to a set signal on which both sinusoidal fitting and lock detection methods are used to extract the phase. At each noise level, 100 tests were performed with randomized noise. The lock-in method performs calculations in approximately half the time of the sine fit method.

FIG. 12B is a graph of absolute phase difference |Δφ| versus noise factor N for the lock-in method (L or black curve) and the sine method (S or gray curve). Figure 12B shows that both methods maintain approximately the same level of accuracy and precision across all tests.

The locking method removes the need to predict the sinusoidal parameters used for the fit. The only fit performed is that of the cosine wave to the low-pass filter constant, which is so constrained that it almost never produces a bad fit. However, if a sine fit is used, it has been found to perform much more accurately when the sine wave fitted to the data has a constant period. If the period can be fitted with other parameters, the processing time is longer and the results are often less accurate.

LSP Noise reduction in measurement results

Extracting the second stress characteristic using LSP measurements from the LSP subsystem 200 consists of two main parts: a data acquisition part and a data analysis part. In the data acquisition portion of the measurement results, the scattered LSP beam 216S is imaged according to the input polarization state of the initial LSP beam 216 from the LSP light source 212 . Imaging is achieved by recording at digital detector 246 the intensity of scattered light from stress-induced features (eg, refractive index changes) within the bulk of CS substrate 10 caused by one or more 10X processes.

The recorded LSP image 248 is processed by the system controller 400 to extract the intensity along the laser beam, which is analyzed for the input polarization to extract the amount of optical delay between two orthogonal states of the beam. Stress profiles are reconstructed by modeling the observed delays. Therefore, the quality of LSP measured stress profiles is fundamentally limited by the noise in the imaging process, which is usually dominated by laser-based noise. An example of such laser-based noise is speckle, which arises from the high coherence of the LSP light source 212, as well as from imperfections in the optical surfaces (roughness, flatness, etc.) Uniformity and inhomogeneity, etc.).

During the propagation of the LSP beam 216 through the LSP subsystem 200, the interaction of the LSP optical (laser) beam 216 with defects in the system results in random amplitude and phase variations within the beam wavefront. When the LSP beam 216 is coherently imaged by Rayleigh scattering, the wavefront distortion causes a static interference pattern (called a speckle pattern) in the image plane by large Characterized by changes in intensity. Strength deviations from the desired signal are seen as noise in the LSP measurement results. To reduce the effect of laser speckle, imaging can be averaged within individual speckle patterns by modulation of polarization, amplitude or phase in the beam wavefront.

In one embodiment, laser-based noise is reduced in the LSP subsystem 200 by passing the initial LSP light (laser) beam 216 through the movable light diffuser 222, which is Examples may include holographic diffusers. This "stirs" the beam rays within the diffuse angle according to the local structure of the diffuser. To minimize beam divergence due to this "ray churn", a movable optical diffuser 222 is placed in the image plane of the Kepler telescope configuration, as shown in the exemplary configuration of FIG. 4A. The LSP beam 216 is first focused onto a movable light diffuser 222 by a first focusing lens 220 , and the transmitted beam is recollimated by a second focusing lens 224 .

下產生數位偵測器246處的基於雷射的雜訊(例如，斑點圖案)的變化。雜訊平均的最大效果在

＞ 1的條件下達成，其中t _C係數位偵測器246的曝光時間。此條件亦消除成像中的潛在消隱，該潛在消隱係由跨可移動光漫射體222的光學透射變化造成。實施基於漫射體的雜訊減少改良了光學延遲的量測。這在第13A圖及第13B圖中示出，第13A圖及第13B圖係光學延遲OR(弧度)與進入CS基板的深度D (mm)的曲線圖。第13A圖的曲線圖係在不使用上述雜訊減少設備及方法的情況下獲得。第13B圖的曲線圖係藉由使用上述雜訊減少設備及方法獲得。第13B圖的曲線圖的平滑度係應用本文所揭示的雜訊減少設備及方法的直接結果。 Alleviating the divergence of the LSP beam 216 after undergoing light diffusion provides a more efficient (ie, less aberrated) focused LSP beam 216F at the CS substrate. Using the movable light diffuser 222, at the rotational speed of the spinning diffuser

A change in the laser-based noise (eg, speckle pattern) at the digital detector 246 is generated below. The maximum effect of noise averaging is at

> 1, where t _C is the exposure time of the detector 246. This condition also eliminates potential blanking in imaging caused by changes in optical transmission across the movable light diffuser 222 . Implementing diffuser-based noise reduction improves optical delay measurements. This is shown in Figures 13A and 13B, which are graphs of optical retardation OR (radians) versus depth D (mm) into the CS substrate. The graph of FIG. 13A was obtained without the use of the noise reduction apparatus and method described above. The graph of Figure 13B was obtained using the noise reduction apparatus and method described above. The smoothness of the graph of FIG. 13B is a direct result of applying the noise reduction apparatus and methods disclosed herein.

Use bend points and CS base plate mid-plane OR graph offset

Since the location of the top surface 12 of the CS substrate 10 may be difficult to determine from the LSP image 248, the stress profile may be shifted to the appropriate location based on the general shape of the retardation curve (OR and D). The OR delay curve has two bending points where the derivative is zero. Exemplary actual OR and D curves and two bending points BP1 and BP2 are shown in Fig. 14A. Data points are shown as open circles. The two bending points correspond to where the stress profile changes from compression to tension, or vice versa.

If the stress profile is symmetric, the two bending points BP1 and BP2 should also be symmetric about the mid-plane MP (see FIG. 1A ) of the CS substrate. Therefore, if the thickness TH of the CS substrate 10 is known and the two bending points BP1 and BP2 of the optical retardation OR curve can be found, the OR profile can be horizontally shifted to the correct position. This allows for a more accurate determination of the depth of compression, DOC, since the location of the top surface 12 of the CS substrate 10 is chosen based on the known symmetry and thickness of the CS substrate. Figure 14B is similar to Figure 14A, but shows an OR curve shifted to the left compared to Figure 14A using the graph shift (data shift) technique described above.

Use curve fitting to make OR graph offset

An alternative method of extracting DOC for a symmetric stress profile involves analyzing the shape of the retardation profile (ie, the OR vs. D curve). If the thickness TH of the CS substrate is known and the relative positions of the bending points BP1 and BP2 can be determined by polynomial fitting, the compression depth DOC of the CS substrate can be determined by the following expression: DOC =[TH - (BP2 - BP1)]/2 Where BP1 and BP2 are the relative depth positions of the bending points.

for OR and D. Curve Fitting of Curves

Embodiments of the present disclosure relate to a method of obtaining a good fit to OR and D curve data. The method includes employing a combination of linear and quadratic functions to obtain a curve fit. This method is hereinafter referred to as the LinQuad method.

Figure 15A is a graph of OR versus D data (circles) and shows an exemplary fitted curve FC (solid line) to OR data using the LinQuad method. The LinQuad method assumes the following model stress function, where σ is the stress, x is the depth coordinate into the CS substrate 10 and R is defined below:

其中 d _l 為線性區的深度， d _c 為彎曲區的深度， C ₀ 為恆定乘數且 t為CS基板厚度。 The corresponding delays can be extracted and fitted to the original data of interest to regenerate the stress profile. Here, C denotes the normalized modeled ion concentration in the CS substrate. Its expression is as follows.

where _dl is the depth of the linear region, dc is the depth of the curved region, _C0 is a constant multiplier and _t is the CS substrate thickness.

此處， CT為應力輪廓的中心張力，且

為約60

的(部分任意的)常數。真LinQuad函數在上文界定，其中僅擬合了 d _c 、 d _l 、 C ₀ 。然而， σ( x)的此最後表達式允許第四個參數(即，中心張力 CT)變化，這可幫助函數更緊密地擬合資料。 The substitution expression is given by:

Here, CT is the central tension of the stress profile, and

is about 60

A (partially arbitrary) constant for . The true LinQuad function is defined above, where only d _c , d _l , C ₀ are fitted. However, this last expression for σ ( x ) allows the fourth parameter (ie, central tension CT ) to vary, which can help the function fit the data more closely.

Figure 15B is a plot of stress S(x) = σ ( x ) versus depth D (mm) based on the LinQuad fit of the OR and D curves of Figure 14A.

power spike function

其中 CT _sp 為尖峰區R1中的尖峰的中心張力， mid為厚度 TH的一半， CS _sp 為尖峰的壓縮應力，且 DOL _sp 為尖峰的層深度。參數 L _eff 為尖峰區R1的有效長度(深度)。此函數為在末端處具有兩個誤差函數尖峰的功率輪廓的拼接。 Cs _sp 及 DOL _sp 值特定於每一玻璃類型且作為常數被輸入。僅有的需要擬合的參數為函數的功率 p及峰值中心張力 CT _P 。 The power spike function is defined as:

where CT _sp is the central tension of the spike in spike region R1, mid is half the thickness TH , CS _sp is the compressive stress of the spike, and DOL _sp is the layer depth of the spike. The parameter L _eff is the effective length (depth) of the peak region R1. This function is a concatenation of power contours with two error function spikes at the ends. Cs _sp and DOL _sp values are specific to each glass type and are entered as constants. The only parameters that need to be fitted are the power p of the function and the peak central tension CT _P .

FIG. 16A shows an OR vs. D plot of an exemplary fitted curve FC using a power spike function. FIG. 16B is a graph of the stress profile S(x) (MPa) versus the depth D into the CS substrate 10 based on the power spike fitting of the OR and D curves in FIG. 16A .

Remove systematic errors to conform to symmetrical stress profiles

The stress profile of the CS substrate using LSP measurement data was obtained by differentiating the OR and D curves. Thus, a symmetric stress profile will always correspond to an asymmetric OR vs. D curve. However, systematic errors from various components in the LSP subsystem 200 can introduce symmetric components into the OR and D delay data, preventing accurate extraction of stress profiles. This effect can be mitigated by decomposing the delay data into symmetric and antisymmetric components, and fitting only the antisymmetric part (ie, the asymmetric data points).

其中 f _s 及 f _a 為延遲 f的對稱分量及反對稱分量，且由以下方程式表達：

Considering the optical retardation OR in the form of a function f(x) , the decomposition can be achieved as follows.

where f _s and f _a are the symmetric and antisymmetric components of the delay f and are expressed by the following equation:

Figure 17A is a fit to an OR vs. D plot based on initial OR data, while Figure 17B is a fit to an OR vs. D plot with the symmetric component of the data removed using the method described above. The fitting error of the fitting curve FC to the measurement data in Fig. 17B is 0.006, while the fitting error in Fig. 17A is about 0.46.

for accurate CT and DOC The adjustable fitting area of

A single fit to the OR and D curves may not always be sufficient to accurately determine central tension CT and depth of compression DOC. This is because scattering from the LSP coupling interface 42B or the coupling interface INT2 can hinder data collection close to the top surface 12 of the CS substrate 10 .

In the example, the fitting to the OR and D curves was performed using multiple fits to separate regions of the curve associated with central tension CT and depth of compression DOC and the range of fits for the OR data was adjusted for accurate CT and DOC extraction.

Figures 18A and 18B show exemplary OR and D curves where the region around the bending points BP1 and BP2 defined by the data (circles) was fitted to extract the depth of compression DOC. Fig. 18B shows the central linear region between bending points BP1 and BP2, which is fitted to extract the central tension CT. In both cases, the range of OR vs. D data is substantially reduced to that portion of the OR vs. D curve associated with a given stress parameter.

Figures 19A-19D further illustrate the effect of data range selection (shown by the vertical dashed lines) on the quality of the fit. Figure 19A is a graph of OR vs. D where the complete data range is considered and where the fitted curve does not fit the bend points BP1 and BP2 very closely. Fig. 19B is a corresponding graph of stress S(x) versus D (depth) for Fig. 19A showing compressive stress CT and depth of compression DOC.

Figure 19C is a graph similar to the OR vs. D curve of Figure 19A, except that the data range is reduced to the area between the vertical dotted lines, and thus the first "end" area ER1 and the second "end" of the measured data are omitted. "End" region ER2. The fitting curve FC of FIG. 19C closely follows the bending points BP1 and BP2. The corresponding S(x) and D curves are shown in Figure 19C, and the values of compressive stress CT and compression depth DOC are substantially different from those of Figure 19B, which use the complete Data range. Simultaneous EPCS and LSP measurement considerations

One way to achieve good accuracy in depth of compression (DOC) measurements using the LSP subsystem 200 is to press the CS substrate 10 against a stop surface (e.g., support plenum 70 ) to secure the top surface of the CS substrate 10 12 is coplanar with a predefined surface, which can be assigned a depth z=0. This pressing can be achieved by pushing the CS substrate 10 against a stop, or by applying a vacuum such that ambient atmospheric pressure provides the force to push the top surface 12 of the CS substrate 10 into place at z=0 (see eg Figure 8A, Figure 8B).

On the other hand, achieving a sharp (i.e., high-contrast) mode spectrum 160 using the EPCS subsystem 100 for accurate stress measurements in the near-surface region R1 of the NSWG 18 also often requires good CS substrate flatness in the EPCS measurement region. This can also be achieved using a vacuum system 91.

Since the EPCS and LSP measurement regions are located at different locations on the CS substrate, applying vacuum at the LSP measurement region can in some cases deform the CS substrate at the EPCS measurement region and result in suboptimal Or even poorly flat or significantly deformed surfaces. This results in the EPCS mode spectrum 160 having poor contrast and being "out of focus". These conditions can lead to reduced accuracy and reduced precision, as well as measurement failures, since poor contrast can cause the system controller to fail to identify some target features of the mode spectrum 160 used to perform stress calculations.

In an exemplary embodiment, the EPCS detector system 140 of the EPCS subsystem 100 utilizes adaptive focusing to achieve proper alignment of the CS substrate 10 on the support plenum 70 to be aligned at the CS substrate to obtain the LSP subsystem The best (most accurate) DOC measurement results and near-surface stress measurement results are obtained when the EPCS subsystem is used for the best LSP measurement results of 200.

In one embodiment shown in FIG. 20, this is achieved by making the focusing lens 142 of the EPCS detector system 140 adjustable (e.g., by mounting the focusing lens on a translation stage 143 to make it axially movable. ), the translation stage 143 is operatively connected to and controlled by the system controller 400 in an example. In an example, translation stage 143 includes precision linear actuators, such as piezoelectric actuators. In another example, translation stage 143 includes a ball screw actuator. This allows the focusing lens 142 to translate along the second optical axis A2 to improve or maximize the contrast of the mode spectrum 160 captured by the EPCS digital detector 150 . In an example, the contrast of the mode spectrum 160 is improved to enhance target spectral features, such as TM stripes 163TM and TE stripes 163TE and critical angle transitions 166TM and 166TE.

The position of the axially movable focusing lens 142 may be electronically monitored by the system controller 400 to calibrate the EPCS subsystem by taking into account the "optical path length" or OPL (e.g., the distance from the focusing lens 142 to the EPCS digital detector 150) calibration. In one embodiment, considerations can be simplified as long as the OPL is not outside a predefined acceptable range such that the initial calibration is still accurate. In another embodiment, the calibration is corrected based on the OPL, and the surface stress S(0)=CS and/or depth of layer DOL are calculated based on the corrected calibration.

In another embodiment, the focusing lens f1 has a variable effective focal length that is actively controlled by the system controller 400 to obtain the high contrast mode spectrum 160 when the specimen is aligned to ensure the depth of compression DOC of the LSP subsystem 200 The most precise or accurate measurement results. The variable focal length focusing lens 142 may comprise a compound lens (similar to a photographic multi-component lens having more than one optical element), or may additionally comprise an adaptive lens, such as a fluid-filled lens, where changing the pressure of the fluid changes the shape of the lens and So change the focal length. When using a variable focal length focusing lens 142, it may not be necessary to shift the position of the focusing lens 142, since varying the focal length may in many cases be sufficient to compensate for deformations in the specimen shape in the EPCS measurement region due to alignment sample to obtain the best measurement results in the LSP measurement area.

In another embodiment, the variation of the effective focal length of the focusing lens 142 can be accomplished by an adaptive lens surface in the form of a mirror that can be combined with a fixed singlet to produce a net effective focal length that can be varied over a range, even when When the CS substrate alignment is optimized for the LSP subsystem 200 , this range is sufficient to produce the high contrast mode spectrum 160 .

Because deformations in the CS substrate 10 tend not to be large, changes in the refractive power of the variable focus focusing lens 142 do not need to be particularly large to compensate. In an example, the focal length of focusing lens 142 may be changed by up to 15%, or in another example by up to 10%.

On the other hand, when the CS substrate 10 has a thickness of less than 0.6 mm, it may be necessary to change the refractive power by more than 15%, and as much as 20% or even 25%. Thus, in an example, the adaptive system for changing the focal length of focusing lens 142 is configured to change the focal length over a range of focal lengths representing 25% of the average focal length, although in many cases 20% of the average focal length , 15%, or even 10% might suffice.

Similarly, because the focusing lens 142 system is focused at infinity for measurements on flat CS substrates, the focusing The range of axial positions accessible to the lens will ideally represent about 25% of the focal length of the lens, although in some cases 20%, 15%, or even 10% of the focal length may represent a sufficient range of positions.

21A and 21B are schematic diagrams of an exemplary embodiment in which two or more focusing lenses 142 with slightly different focal lengths are mounted on a support member 152 to define a focusing lens assembly 153 . The support member 152 is movable to place a selected one of the focusing lenses 142 in the optical path of the reflected EPCS beam 116R (ie, along the second axis A2). This allows the user to select the focal length of the focus lens 142 from a set of discrete focal lengths. Figure 21A shows an example where the support member 152 is in the form of a rotatable wheel that is rotatable about the axis of rotation AW. Figure 21B shows an example where the support member 152 is in the form of a linearly translatable support frame. For example, focusing lens 142 is shown. In general, the focusing lens assembly 153 can support two or more focusing lenses 142 .

If the contrast of the features of interest in the mode spectrum 160 (eg, TM mode line 163TM and TE mode line 163TE and TM critical angle transition 166TM and TE critical angle transition 166TE, etc.) is deemed sufficient, then the measurement proceeds as usual. If the contrast of the feature of interest is deemed insufficient, focusing lens 142 with a different focal length is moved into the optical path of reflected EPCS beam 116R and a new mode spectrum 160 is captured by EPCS digital detector 150 and analyzed for contrast. This process is repeated until a mode spectrum 160 with sufficient contrast is obtained.

In an example, the difference in focal length of focusing lenses 142 may be set by the total desired focal length coverage and the total number of lenses on the support member. In one example, six focusing lenses are supported by the support member, and the focusing lenses cover a range between 20% and 30% of the average focal length of the entire set of focusing lenses, and the focal lengths are spaced between 3% and 7% of the average focal length %between.

In another example, the focal lengths are not uniformly spaced such that the spacing of each pair of adjacent focal lengths is approximately a fixed percentage of the average of the adjacent focal lengths, where the percentage is between 2% and 20%, and more preferably Between 3% and 10%.

In another related embodiment, some or all of focusing lenses 142 comprise Fresnel lenses. In another embodiment, the focusing lenses 142 need not have different focal lengths, but may be positioned on the movable support member in such a way that when the selected focusing lens is placed in the optical path, the focusing lens is at a distance from the EPCS. The distance of the digital detector 150 is different from other focusing lenses. In this embodiment, obtaining a spectrum with sufficient contrast for the features of interest is not necessarily guaranteed by a custom selected focal length with a complete set of discrete dense intervals, but rather by a set of distances from the digital detector and /or can be guaranteed by focal length. This can reduce the cost of the EPCS subsystem 100 by utilizing standard off-the-shelf focusing lenses and positioning each focusing lens to produce a sharp image for the specific warp/curvature range of the CS substrate 10 .

In an example, the system controller 400 may be configured to select one of the focusing lenses 142 based on a measure of the contrast of the feature of interest of the captured pattern spectrum 160 .

In another embodiment, measurements can be made by using the two or three better mode spectra 160 with the best contrast among all captured mode spectra, and then the better result can be calculated as the two or three Average of the spectrum of the preferred mode. In an example, the preferred result can be calculated as a weighted average of the two or three preferred mode spectra. In a related example, the weight of each preferred spectrum may be proportional to the contrast of the feature of interest of the preferred mode spectrum.

Stress measurement calibration using independent stress measurements

The EPCS subsystem 100 may be very good at obtaining high-contrast mode spectra 160 of CS substrates formed using Li glass by a 10X process (e.g., where K ions replace Li and/or Na ions from the glass in the near-surface region). This in turn allows good measurements of the inflection point stress CS _k by measuring the birefringence based on the relative positions of the TM critical angle transition 166TM and the TE critical angle transition 166TE (see FIG. 3B ).

On the other hand, EPCS measurements of inflection point stress CS _k often have lower relative precision than measurements of surface stress S(0). In particular, measurements of inflection point stress _CSk often have a standard deviation of a few percent of their mean value, while surface stress S(0) often has a standard deviation of about 1% to 2% of their mean value. In addition, the value of the inflection point stress CS _k obtained simply as the ratio of the detected birefringence B of the critical angle to the stress-optic coefficient (SOC) is comparable to that obtained from constructive RNF measurements of the stress profile The value of the inflection point stress CS _k is slightly different.

When the EPCS measurement of the inflection point stress _CSk is considered less accurate than it could or should be, this may be due to systematic errors in the measurement of the birefringence at the critical angle. This systematic error can be caused by the TM mode line 163TM and the TE mode line 163TE being too close to the TM critical angle transition 166TM and the TE critical angle transition 166TE, and further caused by the specific shape of the TM and TE refractive index profiles.

When making quality control measurements, such systematic errors are mitigated by calibrating the EPCS-based measurement of the inflection point stress _CSk with a corresponding independent reference stress measurement that can be derived from the same Destructive measurements on a set of CS substrates formed by a process or selected from the same batch during that same process. In an example, this is achieved by applying a calibration multiplier K _cal based on independent measurements via the following relationship: CS _k (EPCS, calibrated) = K _cal • CS _k (independent). In an example, the calibration multiplier Kcal can be used as a general calibration factor for the stress profile calculated by the EPCS subsystem 100 via the following equation: S( _EPCS , calibrated)=Kcal S(original) where S(orig) is the original Measured (uncalibrated) stress profile S(z).

Extraction of tension band stress profile

The 10X process used to form the CS substrate 10 forms a compressed band that bounds the NSWG 18. This band of compression extends into the substrate and reaches a zero value, which defines the depth of compression DOC. Beyond the DOC, the compression band ends and the tension band begins.

If the stress profile in tension bands can be accurately extracted, and it can be used as a powerful tool to help extract a substantially accurate representation of the stress profile in compression bands. This can be done by force balancing utilizing the stresses in the entire CS substrate 10 or in half of the CS substrate (ie a so called "half force balancing").

In one embodiment, in addition to the area of the stress profile in the tension band (represented by the depth integral of the tensile stress from one depth of compression to the depth of compression on the opposite side), also obtained from LSP-based measurements in reliable Slope extracts reliable values for the slope of the stress profile at depth.

In an example, the depth of reliable slope extraction may be the depth of compression DOC. In the compressive stress region, the surface compressive stress is determined by the EPCS method. In some cases, compression is also extracted from EPCS methods using prior techniques such as IWKB, or linear profiles, erfc-shaped profiles, or exponential profiles, or LinQuad profile approximations, when there are not enough guided patterns for reliable IWKB extraction. part of the stress profile. The EPCS-based method then provides a target attachment point, either at the surface with a surface stress value S(0), or at a deeper attachment point (e.g., inflection point depth z _k ; see Fig. 1B ), up to this attachment point, The surface portion of the stress profile S(z) can be provided from EPCS measurements. In the latter case, the inflection point stress CS _k may not be specified with high accuracy due to limitations of EPCS measurements.

However, this value of inflection point stress _CSk may provide a sufficient starting point for iterative refinement to extract the stress profile in a compressive zone (eg, substantially zones R1 and R2 in FIG. 1B ). In the first iteration, a second-order polynomial can be used to connect near-surface junctions with surface stress values S(0) to deep junctions (eg, inflection point stress _CSk or depth of compression DOC) with reliably extracted stress slopes. This determines a first approximation of the stress profile in the compressive zone with the first part obtained from the EPCS up to the first junction point (e.g. at inflection depth z _k ) and obtained via polynomial interpolation between the two junction points The second part of , where at the second connection point, not only the surface stress S(0), but also the stress profile slope is matched.

In a particular example, the second connection point may be a compressed depth DOC, but need not be. A first approximation of the stress profile S(z) is integrated. If the stress profile is not symmetrical, EPCS measurements can be performed on both sides of the specimen and a first approximation of the stress profile is obtained as above for each side. If the stress profile S(z) is symmetrical by design and implementation, it can be assumed that the rear side of the specimen has the same stress profile in the rear compression zone as in the front compression zone.

A first approximation of the stress profile from both the anterior and posterior compression zones was integrated with respect to depth over the respective compression zones and compared to the depth integral of the tension over the tension zone. If the absolute value of the difference is greater than a predefined acceptable limit, a correction step is performed to reduce the difference. In the example, the predefined acceptable limit is 5% of the stress area of the tension band, but progressively better acceptable limits include 3%, 2%, 1% and 0.5%.

Acceptable limits may be determined based on an estimate of the accuracy of extraction of the tension band stress profile. In one embodiment, several first approximations of the stress profile are obtained by different methods, all matching the inflection point stress CS _k at the first connection point, and the stress value and the stress at the second connection point (e.g., depth of compression DOC) slope. Different types of first approximations may include second-, third-, and fourth-order polynomials, exponential profiles, erfc-shaped profiles, Gaussian profiles, and Lorenz profiles. Then, for each of these first approximations, the difference is found between the stress area in the compression band of the first approximation and the stress area in the tension band extracted using the LSP-based measurements. A linear combination of these first approximate stress profiles is then found such that the stress area of the linear combined stress profile is equal to the tension band stress area.

In another embodiment, the limited accuracy of EPCS-based measurements of inflection point stress _CSk is accounted for by allowing the range of inflection point stress _CSk to be targeted around the initial EPCS-based estimate of inflection point stress _CSk . In a first approximation of the compressive stress portion of the stress profile, a preferred target shape function for the interpolated region of the compressive band is used, concatenated with an EPCS-based initial value of the inflection point stress _CSk . In an example, the preferred target shape is a second order polynomial.

After each iteration, the stress area from the compressive stress profile of the two combined compression bands (one on each side of the specimen) was subtracted from the stress area of the tension band. If the absolute value of the difference is greater than the target predefined acceptable limit, the target value of the inflection point stress CS _k can be changed within the predefined acceptable range of the inflection point CS _k according to the available EPCS-based method The estimation accuracy of the obtained inflection point stress measurements was determined.

In an example, the estimated inflection point stress accuracy is about 10 MPa, but in some cases better 7 MPa or 5 MPa or 3 MPa. When no surface spikes are present and guided mode is not available, then the same technique can be used to connect to the target surface stress S(0), which is allowed to be determined by the accuracy of the surface stress measurements changes within the range.

In an example, the range of acceptable values for the target surface stress S(0) or the inflection point stress CS _k may be up to 6 standard deviations wide, for example, 3 on either side of the measured value of the surface stress or inflection point stress standard deviation. In one embodiment, the target surface stress S(0) does not need to be varied iteratively, but can be calculated algebraically using the measured area difference between the first approximate stress profile and the tension band stress profile and the interior for the compressive stress region The optimal function form selected by the interpolation part is determined.

strengthen EPCS subsystem

FIG. 22A is similar to FIG. 3A and shows an example of an enhanced EPCS subsystem 100 . The enhanced EPCS subsystem 100 places the EPCS light source 112 at a remote location relative to the EPCS coupling port 42A. Remote EPCS light source 112 is multi-wavelength and may include one or more light source elements 123 (eg, 123a, 123b, 123c...) that respectively emit light at different wavelengths _λa , _λb , _λc .... The multi-wavelength EPCS light source 112 may also include a single light source element 123 that emits broadband light, where the different wavelengths are within the broadband spectrum or at different positions within the broadband spectrum.

EPCS light source 112 is optically connected to focusing optics 121 by a light guide 130 having an input end 131, an output end 132, and an axial length AL (see close-up inset of extended light guide 130 at bottom of figure). In an example, focusing optics 121 may include one or more lens elements. In an example, focusing optics 121 may be color corrected, ie, designed to image multiple wavelengths without substantial chromatic aberration. This can be achieved using achromatic lenses and optical coatings designed for the wavelength or wavelength range used.

In an example, light guide 130 may comprise a liquid-filled light guide, such as available from ThorLabs Corporation of Newton, New Jersey as part number LLG5-4T. In another example, the light guide 130 may comprise a fiber optic bundle or a solid light pipe. Exemplary light guide 130 has an axial length AL of at least several inches and preferably 8" or more, where the exact length is determined by the location of distal EPCS light source 112.

An EPCS light beam (hereinafter light or light beam) 116 from the distal EPCS light source 112 is coupled into the input end 131 of the light guide 130 and travels therein as guided light 116G. Optical coupling can be facilitated by the use of one or more lens elements 135 (see FIG. 23). Guided light 116G travels to output end 132 of light guide 130 and is emitted as initial EPCS beam 116 . This initial EPCS beam 116 emitted from the output end 132 of the light guide 130 is divergent. This diverging light is received by focusing optics 121, which forms three forms of focused EPCS beam 116F, which is directed to EPCS coupling beam 42A. The remainder of the exemplary EPCS subsystem 100 of Figure 22A is as described above in connection with Figure 3A. The light guide 130, the lens element 135, and other optional optical components between the light source and the light guide 130 (such as the diffuser 137 introduced and discussed below) make up the light guide assembly that integrates the EPCS from the EPCS light source 112. Beam 116 (sequentially filtered or multi-wavelength) is delivered to focusing optics 121 residing near EPCS coupling beam 42A.

Figure 22B is similar to Figure 22A and shows an embodiment in which the split TM-TE polarizer 148 is replaced by a switchable TM-TE polarizer 148S. The switchable TM-TE polarizer 148S is controlled by a polarizer controller 149 operatively connected to the system controller 400 . In this configuration, the EPCS digital detector 150 detects the TM mode spectrum 161TM and then the TE mode spectrum 161TE sequentially for each wavelength, rather than for each wavelength when using the split TM-TE polarizer 148 of FIG. A wavelength detection combined TM-TE mode spectrum 160 (see FIG. 3B). This approach increases the number of detector pixels available for the mode spectrum images 161TM and 161TE and eliminates some of the resolution that occurs at the boundary between the combined TM-TE mode spectrum 160 when using the split TM-TE polarizer 148 Ratio/contrast issues. The exemplary switchable TM-TE polarizer 148S comprises a magnetically charged polarizing crystal as is known in the art of polarization switching. The analysis of the mode spectrum images 161TM and 161TE captured sequentially is the same as the analysis of mode spectrum images captured simultaneously using the fixed TM-TE polarizer 148 .

FIG. 23 is a schematic diagram of an exemplary embodiment of a remote EPCS light source 112 . The exemplary remote EPCS light source 112 includes a plurality of light source elements 123, with three light source elements 123a, 123b, and 123c shown as an example. Exemplary light source elements 123a, 123b, and 123c emit light beams 116a, 116b, and _116c having respective wavelengths _λa , _λb , and λc, respectively. Beams 116a, 116b, and 116c are directed to travel along a common source axis AS using wavelength selective elements 125a and 125b, which in the example are configured to transmit light of one wavelength band and reflect another. A dichroic mirror for light in a wavelength band. In an example, beams 116a, 116b, 116c combine to form a single multi-wavelength EPCS beam 116 .

In an example, the light source element 123 is operatively connected to and controlled by the system controller 400 , or is controlled by a light-source-element (LSE) controller 405 operatively connected to the system controller 400 control. The light source elements 123 may be activated simultaneously or sequentially, as discussed in more detail below. The light source elements 123 need not be narrowband and in examples may collectively generate relatively broadband light to provide a relatively wide range of measurement wavelengths, such as in the near UV to near IR range.

With continued reference to FIG. 23, the exemplary light source system further includes an optical filter device 500 such as that disclosed in U.S. Provisional Patent Application No. 63/002468, filed March 31, 2020, which is incorporated by reference in its entirety. into this article. FIG. 24A is a front view of a portion of optical filter device 500 , referred to as filter wheel 530 . The filter wheel 530 includes a support member 510 operable to support two or more apertures 516 each containing two or more optical filter assemblies 600 for an integer number m The optical filter assembly can be denoted as 600a, 600b...600m. The different optical filter assemblies 600a, 600b, 600c, 600d ... 600m each have a filter axis AF and are configured to operate within a corresponding relatively narrow bandwidth δλ _a , δλ _b , δλ _c , δλ _d ... δλ _m Narrowband optical filtering of the EPCS beam 116 is performed at respective wavelengths λ _a , λ _b , λ _c , λ _d . . . λ _m of respective wavelengths (such as, for example, 2 nm). Optical filter device 500 is thus configured to perform narrowband optical filtering using optical filter 600 such that relatively broadband light of a given wavelength (e.g., greater than 3 nm or greater than 5 nm, or greater than 10 nm or greater than 20 nm) is included. , etc., and including extremely broadband light with bandwidths of 100 nm or hundreds of nm) can be narrowband filtered around this wavelength. In the discussion below, light that has passed through one of the optical filter assemblies is referred to as filtered light. Filtered light is narrowband and has a center wavelength defined by the filters it passes through.

Figure 24A shows an exemplary filter wheel 530 in which the support member 510 supports four different optical filter assemblies 600 (600a, 600b, 600c, and 600d) with corresponding narrowband filtering The detector (center) wavelengths λ _a , λ _b , λ _c and λ _d . The exemplary support member 510 of FIG. 24A has a disc-shaped body with a central axis AW, a central section 512, and an outer section 514 in which the optical filter assembly is supported, and in the example uniformly Distributed on the outer segment. The support member 510 also has an outer perimeter 523 , a front side 522 and a rear side (not shown). The central axis AW passes through the central section 512 of the disc-shaped body, as shown. The combination of the support member 510 and the optical filter device 500 constitutes a filter wheel 530 .

Referring again to FIG. 23, the drive system 540 is mechanically connected to the support member 510 and configured to cause the support member to move. An exemplary drive system includes a drive shaft 544 with one of its ends attached to the central section 512 of the support member 510 and the other end of which is attached to the drive motor 550 . The drive shaft 544 is disposed coaxially with the support member axis AW. The drive motor 550 is electrically connected to the system controller 400, which is configured (e.g., using control software) to control the operation of the drive motor 550, such as using motor control signals, while also receiving information including information about the operation of the motor. A data signal for information such as the rotation rate of the filter wheel 530, the relative rotational position, etc.

Drive system 540 causes filter wheel 530 to rotate about axis of rotation AR, which is coaxial with support member axis AW. The filter wheel 530 is then positioned such that the optical filter device 500 sequentially intersects the source axis AS so that the EPCS beam 116 is sequentially filtered to form a sequentially filtered EPCS beam 116 (i.e., comprising a series of filtered beams 116a, 116b...116m of the EPCS beam), as shown in Figure 23 downstream of the optical filter assembly and in the schematic diagram in Figure 24B. FIG. 24B shows two exemplary sequentially filtered EPCS beams 116, where the top example is formed using four filter wavelengths (116a, 116b, 116c, and 116d) and the bottom example is formed using two filter wavelengths (116a and 116d). 116b) Formation. The sequentially filtered EPCS beam 116 then enters the input end 131 of the light guide 130 . As mentioned above, this can be facilitated by using one or more lens elements 135 operatively disposed between the filter wheel 530 and the input end 131 of the light guide 130 along the source axis AS.

The timing of activation of the light source element 123 and the position of the optical filter assembly 600 are controlled by the system controller 400 so that appropriate portions of the sequentially filtered EPCS beam 116 are filtered. Alternatively, all one or more light source elements 123 can be activated simultaneously to form the broadband EPCS beam 116, with the optical filter arrangement 500 used to sequentially define the filtered beams 116a, 116b...116m, the filtered beams 116a, 116b ...116m enters the light guide 130 and is ultimately directed to the beam assembly 40 as a filtered and focused EPCS beam 116F (see Figure 22A)

In an example, the optical filter apparatus 500 is focus corrected to compensate for different focuses of different wavelength portions of the sequentially filtered EPCS beam 116 , where the different focuses are due to different wavelengths. Focus correction can be achieved through the use of correcting lenses 124a, 124b, 124c... that are configured (e.g., axially positioned, have different optical powers, etc.) so that for each The optical wavelength efficiently couples a given one of the sequentially filtered EPCS beams 116 a , 116 b . . . 116 m into the input end 131 of the light guide 130 . In another example, focus correction may be employed by each optical filter assembly 600 having a filter 620 and a correction member 630 configured for focus correction at a given filter wavelength, as described in Section 23 The close-up insets in the figures are shown and described in detail in the aforementioned US Provisional Patent Application No. 63/002468.

It should be noted that the optical filter device 500 can also be deployed within the EPCS detector system 140 to achieve the same goal of providing narrow-band measurement light at different wavelengths so that measurements can be made at each of a number of different wavelengths. The mode spectrum of a given CS substrate 10 is measured in order to improve the measurement accuracy of the stress-related properties of the CS substrate.

The illumination provided by the EPCS light source system 110 to the EPCS coupled light source 42A may be dictated by the overall system timing employed and the wavelength of interest. In one example, the EPCS light source 112 may include a single broadband light source element 123 such as a halogen bulb, incandescent bulb, xenon bulb, or white LED or laser diode, and rely on the optical filter assembly 600 for wavelength selection and bandpass. In another example, multiple light source elements 123 emitting at different wavelengths may be used to generate light at selected wavelengths, such as in the manner described above. In the illustrated embodiment of FIG. 23 utilizing three light source elements 123 (123a, 123b, 123c) and two wavelength selective elements 125, two of the light source elements can respectively emit short wavelengths in a relatively narrow frequency band and long wavelengths, while the third source element has a relatively broadband emission at intermediate wavelengths. For example, the short wavelength could be 365 nm, the long wavelength could be 780 nm, and the broader wavelength could be a white light device for the human eye comprising a dominant blue (450 nm) LED that includes wavelengths of 450 nm, 510 nm, and 640 nm . These three light source elements 123 can be activated simultaneously and continuously with a simple continuous power supply configuration, thereby relying on the bandpass filter configuration of the optical filter device 500 to pass only the desired (narrow-band) wavelength. Adding control of beam intensity (eg, using a variable optical attenuator) allows optimization of LED output at selected wavelengths. This can be useful to compensate for any wavelength sensitivity of the EPCS digital detector 150 .

In instances where one or more of the light source elements 123 comprise LEDs, the LSE controller 405 or system controller 400 can be configured to provide pulsed operation to extend LED life and reduce the need for heat dissipation, thereby eliminating the need for heat dissipation chip needs and results in a more compact EPCS light source 112 . Pulse control systems for LEDs may include current and/or duration control to allow better matching of light available for bandpass filter transmission and detector sensitivity at a given wavelength. For example, when "white" LEDs are used to provide several different measurement wavelengths, the digital detector exposure time can be aligned with the available light controlled by the LED driver. Pulsed LEDs during the detector exposure time also allow low duty cycle overdrive of the LEDs for higher intensities.

The focused configuration of EPCS subsystem 100 (ie, in which focusing optics 121 form focused EPCS beam 116F) facilitates accurate optical alignment during EPCS metrology of CS substrate 10 with little loss of light. The range of measurement angles relative to the first coupling interface INT1 (see FIGS. 22B and 22C ) is related to the total internal reflection angle. When the CS substrate 10 has a refractive index gradient that generally decreases from the top surface 12 into the bulk 11 of the CS substrate, what is needed to detect the TM mode lines (stripes) 163TM and TE mode lines (stripes) 163TE (see FIG. 3B ) The range of corners is increased but still within a limited range. By optimizing the source and detector viewing angles (i.e., more specifically, enlarging the range of angles in the filtered and focused EPCS beam 116F and thus in the filtered and reflected EPCS beam 116R), Light collection efficiency is increased, resulting in a better image of the mode spectrum 160 for the different wavelengths used.

FIG. 22C is a close-up simplified view of EPCS subsystem 100 near EPCS coupling field 42A, with corresponding portions of EPCS light source system 110 and EPCS detector system 140 showing an exemplary lighting configuration. In particular, a Kohler configuration is employed in which the output end 132 of the light guide 130 is imaged by the focusing optics 121 through the EPCS coupling port 42A onto the entrance pupil EP of the EPCS detector system 140 . In an example, entrance pupil EP resides in focusing lens 142 of EPCS detector system 140, as shown. This configuration ensures that all radiation of the sequentially filtered EPCS beam 116 emitted from the output end 132 of the light guide 130 remains in the EPCS detector system 140 . It also ensures equal illumination across all angles of the EPCS coupling beam 42A, which results in substantially uniform intensities of the TM mode lines (stripes) 163TM and TE mode lines (stripes) 163TE captured by the EPCS digital detector 150.

An alternative configuration focuses the output of multiple light source elements 123 (such as 2d or 3d clusters) at the input end 131 of the light guide 130 to facilitate efficient coupling of the sequentially filtered EPCS beam 116 into the light guide. In the example shown in FIG. 23, a diffuser 137, such as a finite angle diffuser, may be employed at or near the input end 131 of the light guide 130 to improve the light distribution of the sequentially filtered EPCS beam 116 entering the light guide. And the combiner is simplified by eliminating the use of dichroic mirrors.

The measurement method using the enhanced EPCS subsystem 100 is relatively fast and is based on controlling the activation of the light source element 123, the rotational (azimuth) position of the filter wheel 530 of the optical filter device 500 and the exposure time of the EPCS digital detector 150 ( Timing relationship between image capture time). In an exemplary configuration of the enhanced EPCS subsystem 100 used in the experiments, a ThorLabs FW103H high current BSC201 controller with 8-32 taps was used to control the motorized filter wheel 530 . This provides the optical filter device 500 with a (stepped) filter switching speed of between about 55 milliseconds (ms) to 60 ms. In an exemplary experimental configuration, the optical filter assembly 600 has dimensions up to 1" in diameter and 6.35 mm thick. This filter switching speed is still slower than the readout time of the EPCS digital detector 150, the EPCS digital detector The filter 150 can read 100 frames per second in an example, so the filter switching speed is the limiting factor in the measurement speed of the exemplary experimental configuration.

An alternative to a rapidly changing (stepped) filter wheel configuration is to rotate the filter wheel 530 continuously. Rapidly changing configurations require high current drive system 540 to start and stop filter wheel 530 with sufficient precision. The drive system 540 configured to provide constant rotation of the filter wheel 530 uses a relatively small continuous current to keep the filter wheel spinning, while the inertia from the mass of the filter wheel and optical filter assembly 600 keeps the motion sufficiently constant , so that a simple encoder or even simpler reference index sensor can be used to indicate position and even provide a trigger to the EPCS digital detector 150 . A trigger may be used to initiate illumination from the light source element 123 if the light source element 123 is not continuously on. In one example, the exposure time occurs during the duration that the majority (and in another example, the greatest amount) of measurement light passes through a given optical filter assembly 600 . In another example, the exposure time is only when light passes through a given optical filter assembly 600 or when a minimum amount of light (eg, more than 10% of a maximum amount) passes through a given optical filter assembly 600 happens when.

The design of the support member 510 forming the filter wheel 530 may include relatively large opaque regions between adjacent optical filter assemblies 600 . This may allow the opaque region to act like a focal plane shutter and maximize exposure duration across a given mode spectral image for the full size of a given optical filter assembly 600 . Exposure may start when the light is blocked by the opaque region, ie before the optical filter device 500 reaches the light source axis AS and the optical path of the light. Exposure continues as optical filter assembly 600 enters, intersects, and then moves away from light source axis AS. Exposure stops when the optical filter assembly is completely out of the optical path of the light and the next opaque region finally reaches the axis of the light source.

25A and 25B are close-up views of a portion of an exemplary EPCS detector system 140 showing two exemplary configurations of the enhanced EPCS subsystem 100 disclosed herein. An example of the EPCS detector system 140 employs a plurality of EPCS digit detectors 150 , three exemplary EPCS digit detectors indicated at 150 a , 150 b , and 150 c , each of which is operatively connected to the system controller 400 . The three exemplary EPCS digit detectors 150a, 150b, and 150c are spatially separated using a beam splitter 180, which in the example of FIG. 25A may be a conventional beam splitting element. In one example, EPCS digital detectors 150a, 150b, and 150c are used to detect corresponding wavelengths _λa , _λb , and _λc . This can be achieved by placing respective narrowband optical filters 144a, 144b and 144c in front of each of EPCS digital detectors 150a, 150b and 150c. This configuration allows simultaneous detection of mode spectrum images and eliminates the need for optical filter device 500 and its high speed filter wheel configuration, but requires multiple EPCS digital detectors 150 and data synchronization to process simultaneous mode spectrum measurements . The relative axial positions of EPCS digital detectors 150a, 150b, and 150c along the respective optical paths can be set to compensate for any focus differences caused by the different wavelengths of light employed. Likewise, additional focusing lenses 142a, 142b, and 142c may be employed to obtain correct focus at the corresponding EPCS digital detectors 150a, 150b, and 150c.

In the configuration shown in Figure 25B, the beam splitter is a wavelength selective element 125, such as a dichroic mirror, so that selected wavelengths are directed to corresponding EPCS digital detectors. This eliminates the need for a separate narrowband optical filter in front of the EPCS digital detector 150 .

Figure 25C is similar to Figure 25A except that each individual optical filter is replaced by an optical filter device 500 comprising a plurality of optical filters arranged on a filter wheel 530 as described above.

The cost of using a light source system configuration as shown in FIG. 23 using a single optical filter device 500 with a high-speed filter wheel 530 can exceed the cost of using multiple EPCS digital detectors as shown in FIGS. 25A and 25B 150 so that in some embodiments where cost is a factor, the use of multiple EPCS digit detectors may be preferable. The use of multiple EPCS digital detectors 150 has the advantage that the detectors do not need to operate at high frame rates for overall system speed, since the speed comes from using multiple EPCS digital detectors 150 to simultaneously acquire pattern spectrum images. In this case, the exposure time drives the acquisition time, wherein the exposure time is primarily driven by the intensity of the light source element 123 . The use of relatively high power light source elements 123 can be used to reduce exposure time.

Processing the mode spectrum 160 captured at different wavelengths allows for a more accurate analysis of the stress-related properties of the CS substrate 10 . In some cases, the TM mode lines 163TM of a given mode spectrum 160 acquired at one wavelength are clearer (ie, higher in contrast) than the TE mode lines 163TE, and vice versa. Thus, the use of multiple mode spectra 160 captured at different wavelengths allows analysis of the best (highest contrast) TM and TE mode lines. The high contrast mode spectrum 160 allows accurate determination of the positions of the TM mode line 163TM and the TE mode line 163TE. In addition, the positions of TM mode line 163TM and TE mode line 163TE can be interpolated across multiple points within the measurement wavelength range to better determine the true positions of both real and virtual mode lines for extended analysis.

The use of a remote EPCS light source 112 outside the main housing of the hybrid system 20 preserves space within the hybrid system, removes heat sources and provides access to components servicing the light source.

strengthen LSP subsystem

FIG. 26 is similar to FIG. 4A and shows an example of an enhanced LSP subsystem 200 . The LSP light source system 210 of the enhanced LSP subsystem 200 now includes the following components operatively disposed in sequence along the third axis A3 between the LSP light source 212 and the first focusing lens: shutter system 280, rotating half-wave plate 234RH, and Fixed polarizer (with fixed polarization direction) 234F. Shutter system 280 may include, for example, a rotary shutter driven by a drive motor. In an example, LSP light source 212 includes a relatively high power laser diode 213 having an optical output (LSP beam 216) centered at a selected wavelength, such as 405 nm. In various examples, the laser diode 213 has an output power of at least 1 milliwatt (mW), or at least 10 mW, or at least 20 mW, or at least 30 mW, or at least 40 mW, or at least 50 mW.

The optical compensator 230 now includes a spectrometer 260 operatively positioned along a spectrometer axis AS defined by a polarizing beam splitter (PBS) 232 . The optical compensator 230 also includes a fixed half-wave plate 234H and a variable polarizer 234V arranged along the third axis A3 and downstream of the PBS 232 . The variable polarizer 234V is driven by a polarization controller 237 . A movable focusing lens 236 resides downstream of the optical compensator 230 . In an example, movable focus lens 236 is moved by linear motor 272 and is mechanically attached to linear motor 272 by lens mount 270 . In an example, lens mount 270 may comprise a lens tube axially movable (slidable) within a support tube (not shown). In an example, linear motor 272 comprises a linear actuator configured to provide precise linear movement. In an example, the variable voltage 234V includes a liquid crystal variable retarder (LCVR). In an example, temperature controller 235 is in operative communication with variable polarizer 234V to provide temperature stabilization against changes in polarization with temperature.

The use of a relatively high power laser diode in the LSP light source 212 facilitates stress-related measurements on the CS substrate 10 made of a glass material that has an amorphous structure that does not scatter as well as a glass-ceramic material. Crystal structure. The PBS 232 is optimized for efficacy at a selected wavelength (eg, 405 nm) to optimize the amount of light directed toward the CS substrate 10 under test. The combination of half wave plate 234H and PBS 232 allows automatic light intensity control at CS substrate 10, making it possible to alternate between measuring glass CS substrates and measuring glass ceramic CS substrates.

Spectrometer 260 is positioned to receive a portion of LSP beam 216 and perform spectral processing on the LSP beam. Spectrometer 260 serves two main functions. The first function is to monitor the wavelength of the LSP beam 216 in real time, allowing wavelength calibration. The second function is to monitor the change of the output power of the laser diode. Accordingly, the term "spectral processing" may include performing at least one or both of the aforementioned first and second functions.

In an example, temperature controller 235 allows the LCVR of variable polarizer 234V to operate at a slightly elevated temperature (eg, between about 35°C and 40°C) relative to ambient temperature, such as room temperature, thereby reducing the temperature of the room temperature. Fluctuation affects the polarization and improves measurement stability and cycle time. In an example, spectrometer 260 may be a commercially available spectrometer or may be a spectrometer fabricated from standard components known in the art such as a diffraction grating, a series of notch filters, and the like.

A high power laser diode 213 with an output power of about 50 mW may be higher than the required power required to obtain sufficient scattering intensity for certain types of CS substrates 10 . However, the exact amount of LSP beam 216 entering CS substrate 10 can be precisely controlled using rotating half-wave plate 234RH in combination with PBS 232 .

FIG. 27A is a schematic diagram showing an example of how the intensity control of the laser diode 213 is performed. The linearly polarized LSP beam 216 from the laser diode 213 passes through the rotating half-wave plate 234RH and is incident on the PBS 232, which splits the LSP beam into two beams which are directed to the photodetector PD1 and PD2 and are detected by photodetectors PD1 and PD2 , which in turn are operatively connected to system controller 400 . It should be noted that, in practice, additional beam splitters (not shown) may be used to direct portions of LSP beam 216 to photodetectors PD1 and PD2 incorporated into enhanced LSP subsystem 200 . For example, one beam splitter may be placed upstream of spectrometer 260 along axis AS, while another beam splitter may be placed just downstream of PBS 232 .

Fig. 27B is a graph of the normalized optical power OP and the angle θ (°) of the rotating half-wave plate 234RH for the transmission (T) part and the reflection (R) part of the LSP beam 216. An exemplary experimental configuration of polar body 213 was formed from PBS 232 . It can be seen that when the rotating half-wave plate 234RH rotates, the measured power at the photodetectors PD1 and PD2 changes. The mirrored nature of the T and R plots is expected because rotating the half-wave plate effectively rotates the polarization of the light before it enters the PBS 232 . The amount of vertical and horizontal polarization intensity depends on the orientation of the polarization of the LSP 216 from the laser diode.

Referring again to FIG. 26, the movable focusing lens 236 provides a stable solution to focus the LSP beam 216 onto the CS substrate 10 being analyzed at micron resolution. In addition, computer control (via system controller 400 ) ensures repeatability across different mixing systems 20 because the position of focusing lens 236 can be made the same.

The absolute position of the focusing lens 236 can affect the CT (central tension) measurement of the CS substrate 10 . FIG. 28 is a graph of CT (MPa) versus focus lens position LP (mm) (measured relative to a reference position) based on measurements performed on an exemplary CS substrate 10 . The measurement results show about 5 MPa variation of the measured CT across the 2 mm range of motion of the focusing lens 236 . Proper placement of the focusing lens 236 ensures accurate and repeatable stress-related measurements.

Exemplary variable polarizer 234V includes an LCVR driven by polarization controller 237, as described above. During a typical measurement using the LSP subsystem 200, the LCVR is excited by a series of voltages provided by the polarization controller 237 with about 200 milliseconds delay between the voltages. This time delay allows for device response time and image capture and accounts for most of the measurement cycle time. Although LCVRs operate well at room temperature, their response time can be substantially improved (eg, up to a factor of 3) with increasing temperature, thereby reducing response time by reducing the viscosity of the liquid crystal material in the LCVR. In an example, an LCVR is excited with an amplitude-modulated (AM) signal, and an oscilloscope is used to determine the response time of the LCVR. The decreasing trend of LCVR settling time with temperature supports the feasibility of measuring cycle time reduction. Additionally, as noted above, operating at elevated temperatures (e.g., >30°C) relative to room temperature (ambient temperature) reduces or eliminates the effect of temperature fluctuations on polarized light, resulting in multiple independent LSP subsystems 200 higher stability and repeatability.

Exemplary enhancements to the LSP subsystem 200 include a calibration process including camera angle calibration and camera tilt compensation. Figure 29 is similar to Figure 11B, but relevant parameters are labeled differently. The camera angle is denoted as β and is measured relative to the horizontal axis, while _tr is the real CS substrate thickness (which can be measured using, for example, calipers), and _ti is in the image plane (i.e., at digital detector 246 ) of the perceived CS substrate thickness. The camera viewing plane is denoted CVP and the viewing direction is denoted z (z-axis). The camera angle β is related to the parameters t _i and t _r via the relation Cos β = t _i / t _r .

The camera tilt angle θ measures the amount of camera rotation around the z-axis. Deviations in the camera tilt angle θ can change the way the image plane thickness is calculated. As shown in Fig. 29, the calculation of the CS substrate thickness _tr is no longer the vertical distance between the entry point and the exit point, but requires more calculations using trigonometry to take into account the deviation angle θ.

An aspect of the present disclosure includes an enhanced beam centering method for an X-shaped LSP image 248 (including one of the processed images described above) formed from a detected scattered LSP beam 216S involving two two main steps, namely, the improved beam centering step and the improved center point detection step. (See Figure 10A).

1) Enhanced Beam Centering Method

， 其中第一項將光束強度輪廓建模為高斯函數，其中 a 、 b及 c分別為高斯的峰值強度、中心及半徑，而最後兩項對背景強度輪廓(例如，環境光、相機暗計數、不均勻相機響應)建模，其中 d及 f分別為背景強度的斜率及恆定等級。 p為影像中的水平像素的值。然後從 I _M 對 I的最佳擬合發現光束中心為高斯光束的中心。 The improved beam centering method consists of two sub-steps. The first substep finds the beam center along the beam path by modeling the horizontal image intensity profile ( I ) at each depth of the substrate using a model intensity profile ( _{IM )} given by given by

, where the first term models the beam intensity profile as a gaussian function, where a , b , and c are the peak intensity, center, and radius of the gaussian, respectively, and the last two terms model the background intensity profile (eg, ambient light, camera dark count, non-uniform camera response), where d and f are the slope and constant level of the background intensity, respectively. p is the value of a horizontal pixel in the image. The center of the beam is then found to be the center of the Gaussian beam from the best fit of I _M to I.

FIG. 30A is a graph of intensity I(p) versus pixel number p(x) for selected depths along the beam path into CS substrate 10 in the x-direction. The fit estimates the center of one of the scattered LSP beams 216S (i.e., one of the X-shaped LSP images 248; see Figure 4D or Figure 30C, the latter described below), as indicated by the CNTR represented by the large black dot instruct. Once a series of peak centers at each depth along the beam path have been collected, a line fit is applied across all estimated peak centers in a second substep, as shown in the graph of Figure 30B, Figure 30B The plots show peak center fits in terms of pixels positioned along the x and y directions, denoted p(x) and p(y), respectively. The results of this method are compared with actual beam images and shown to locate the center of the scattered beam with high accuracy.

2) Enhanced center point detection

The enhanced center point detection method uses the Gaussian fitting method described above to track the center of the beam. Figure 30C is a schematic diagram similar to Figure 10C showing the LSP image 248 (intensity profile) with two overlapping fitted lines FL1 and FL2 extending through the center of the two line image segments, the two line images Sections are denoted 248-1 and 248-2. The intersection of the two fitting lines FL1 and FL2 represents the center point of the LSP image 248 .

3) Enhancing the entry point method

The parameter of interest of the LSP image 248 is called an entry point and is denoted ENP in Figure 30C. The entry point is determined using the fitted centerlines FL1 and FL2 established by the Gaussian fitting method described above which finds the center of the beam as a function of beam intensity. The entry point ENP is then chosen to be half maximum on the edge intensity profile fitted along the centerline of the LSP image 248 . Figure 30D is a graph of LSP image intensity I(p) versus pixel position p along the fitted line FL2 and near the entry point EP (see Figure 30C). The graph of FIG. 30D shows exemplary edge intensity profiles and identifies maximum intensity I _MAX , minimum intensity I _MIN representing background or zero intensity values (e.g., by shifting the intensity curve), and half-maximum intensity I _1/2 , Half maximum intensity I _1/2 resides midway between I _MAX and I _MIN and defines the location (pixel location) of entry point ENP, which is approximately at pixel 32 in the exemplary graph. Pixels 32 may be related to physical locations on CS substrate 10 to obtain entry points ENP in the coordinate system of the CS substrate.

It will be apparent to those skilled in the art that various modifications may be made to the preferred embodiments of the disclosure as described herein without departing from the spirit and scope of the disclosure as defined by the appended claims. Revise. Accordingly, the present disclosure covers modifications and variations provided they come within the scope of the appended claims and their equivalents.

5, 5A, 5B: Refractive Index Matching Fluids 10: CS substrate 11: Subject 12: Top surface 14: Bottom surface 16: side 18:NSWG 20: Hybrid system 21: Shell 30: Air Curtain 40: Coupling 騜鏡 assembly 42: Commonly coupled 稜鏡 42A: EPCS coupling 騜鏡 42B: LSP coupling 稜鏡 43A, 43B: input surface 44A, 44B: output surface 45A: EPCS Coupling Surface 45B: LSP Coupling Surface 46: 稜鏡Supporting structure 47: thin wall 48: Support frame 48A: EPCS frame section 48B: LSP frame section 49:Mold 49R: Resin 50: Isolation components 52: fastening tab 53: Mounting hole 54: fastening member 60: cover plate 62A: the first hole 62B: Second hole 70: support inflatable part 71: top surface 72: Measuring hole 73: Conveyor element 75: Stable platform 76: surface 80: Movable substrate holder 82: inner lip 90:PV elements or PV pipes (PV rods) 91: Vacuum system 92: Vacuum source 94: stop member 100:EPCS subsystem 110:EPCS light source system 112:EPCS light source 116:Multi-wavelength EPCS beam 116a, 116b, 116c, 116d...116m: filtered beam 116F: Filtered and focused EPCS beam 116G: Guide light 116R: Filtered and reflected EPCS beam 118:Optical polarizer 120: focus lens 121: Focusing optical system 122: light diffuser 123, 123a, 123b, 123c: light source components 124a, 124b, 124c: correction lens 125, 125a, 125b: wavelength selective components 130: light guide 131: input terminal 132: output terminal 135: Lens element 137: Diffuser 140: Light guide assembly 142, 142a, 142b, 142c: focusing lens 143: Translation platform 144: Bandpass filter 144a, 144b, 144c: narrowband optical filters 146: Attenuator 148: TM-TE polarizer 148S: Switchable TM-TE Polarizer 149: Polarizer controller 150, 150a, 150b, 150c: EPCS digital detector 152: Support member 153: Focusing lens assembly 160: Mode Spectrum 161TM, 161TE: TIR section 162TM, 162TE: non-TIR segment 163TM: TM "stripe" or TM pattern line 163TE: TE "stripe" or TE pattern wire 166TM:TM critical angle transition 166TE: TE critical angle transition 180: beam splitter 200: LSP subsystem 210: LSP light source system 212: LSP light source 213:Laser diode 216: LSP beam 216F: Focused LSP beam 216S: Scattered light/Scattered LSP beam 218: Neutral density filter 220: the first focusing lens 222: light diffuser 224: second focusing lens 230: Optical compensator 232: Polarizing beam splitter 234H: The first fixed polarizer 234RH: Rotatable half-wave plate 234Q: one-third wave plate 234V: variable polarizer 235: temperature controller 236: Axially movable focusing lens 237: Polarization controller 240: LSP detector system 243:Collection Optical System 244: Bandpass filter 246: Digital Detector 247: imaging pixels 248: LSP image 248D: Digital LSP image 248C: LSP image profile 248T: Threshold LSP image 260: spectrometer 270: lens holder 272:Linear motor 280: Shutter system 400: System Controller 405: LSE controller 410: user interface 412A: EPCS section 412B: LSP section 500: Optical filter assembly 512: Central section 510: support member 514: External section 516: hole 522: front side 523: Outer perimeter 530:Filter wheel 540: drive system 544: drive shaft 550: drive motor 600, 600a, 600b, 600c, 600d: optical filter assembly 620: filter 630: correction component PD1, PD2: Photodetectors INT1: EPCS coupling interface INT2: LSP coupling interface

The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the detailed description explain the principles and operation of the various embodiments. Accordingly, the present disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1A is a top view of an exemplary transparent CS substrate in the form of a planar sheet.

Figure 1B is an exemplary refractive index profile n(z) and z of an exemplary transparent CS substrate showing a near-surface peak region (R1), a deeper region (R2) and a bulk region (R3), while the inflection point (KN) Located at the transition between region R1 and region R2.

FIG. 2A is a schematic diagram of a hybrid EPCS-LSP metrology system for comprehensive characterization of stress in transparent CS substrates as disclosed herein.

FIG. 2B is a more detailed schematic diagram of the hybrid EPCS-LSP system of FIG. 2A showing an exemplary configuration of the EPCS measurement subsystem and the LSP measurement subsystem.

FIG. 3A is a schematic diagram of an exemplary EPCS subsystem of the hybrid EPCS-LSP system of FIG. 2A.

3B is a schematic diagram of an exemplary EPCS mode spectrum obtained by an EPCS subsystem, wherein the EPCS mode spectrum includes a TM mode spectrum with TM mode lines (stripes) and a TE mode spectrum with TE mode lines (stripes).

4A, 4B and 4C are schematic diagrams of exemplary LSP subsystems of the hybrid EPCS-LSP system of FIG. 2A.

Figure 4D is a close-up view of the LSP image formed on the digital detector of the LSP subsystem, wherein the LSP image includes two line images forming a cross or "X" pattern, and wherein the LSP image and the digital detector form Digital LSP image.

FIG. 5A is a top view of an exemplary canopy support structure for supporting EPCS and LSP coupled canopy.

Fig. 5B is a top view of the cover plate installed on the supporting structure of Fig. 5A.

Figures 6A and 6B are side views of an EPCS and LSP coupled canal supported on a stable platform and illustrate an exemplary method of forming a single molded canal support structure for a coupled canal assembly.

FIG. 6C is a side view of an exemplary coupled-pipe assembly in which the ply support structure is configured such that at least one of the EPCS and the LSP coupled ply is movable in one direction relative to the other (e.g., As shown, z-direction).

FIG. 6D is a schematic diagram of an exemplary hybrid EPCS-LSP measurement system, in which a single coupled beam is used for the EPCS subsystem and the LSP subsystem instead of two separate coupled beams.

FIG. 7 is a cross-sectional view of an exemplary plenum support structure attached to an exemplary support plenum of a mixing system and shows an exemplary movable substrate holder for adjusting measurement positions on a CS substrate.

Figure 8A is a top view of the support plenum showing the gauge holes and pressure-vacuum (PV) rods of the vacuum system operably positioned within the gauge holes to pneumatically engage the CS substrate In order to pull the CS substrate onto the coupling surface of the EPCS and the LSP coupling surface.

Fig. 8B is a close-up cross-sectional view of a support plenum and a measurement hole showing an exemplary configuration of a coupled plenum assembly and vacuum system.

Fig. 9 is a schematic representation of an exemplary user interface as presented by a system controller, wherein the user interface includes an EPCS segment showing an EPCS mode spectrum and an LSP segment showing an LSP line image of a digital LSP image.

FIG. 10A is an example of an LSP section of a user interface showing an exemplary digital LSP image and an intensity histogram of the digital LSP image.

Figure 10B shows exemplary initial or raw digital LSP images and Gaussian blurred ("blurred") LSP images.

Figure 10C shows an exemplary threshold image obtained by applying Ostu's limit to the Gaussian blurred image of Figure 10B.

Figures 10D and 10E show examples of contour detection performed on exemplary Gaussian blurred LSP images.

Figure 11A is a close-up view of the CS substrate and the direction of the focused LSP beam.

FIG. 11B is a close-up view of the edge portion of the CS substrate and shows the viewing angle of the LSP detector system relative to the focused LSP beam.

FIG. 11C is similar to FIG. 11B and shows the scattered light beam reaching the LSP detector system and forming a line image.

Figure 1 ID shows another view of the LSP detector system and CS substrate with the focused LSP beam.

FIG. 11E is a schematic diagram showing dimensions and angles for determining the thickness of a CS substrate.

Figure 12A is the average calculation time T and noise in milliseconds (ms) required to extract the phase φ of the LSP signal with noise for both the lock-in method (blue) and the sine method (green) Factor N.

FIG. 12B is a graph of the absolute phase difference |Δφ| versus noise factor for the lock-in method (blue) and the sinusoidal method (green) for processing a noisy LSP signal.

Figures 13A and 13B are graphs of optical retardation OR (rad) versus depth D (mm) into the CS substrate (the "OR vs. D graph"), where Figure 13A shows the OR data collected with reduction and Figure 13 shows OR data collected by the LSP subsystem using speckle reduction.

14A and 14B are OR and D graphs showing an exemplary method of offsetting the OR data so that bend points BP1 and BP2 are symmetrical about the mid-plane of the CS substrate.

Figure 15A is an exemplary OR vs. D plot comprising discrete data points (circles) and fitted lines to the OR vs. D data points, wherein the fitted line was formed using the "LinQuad" method disclosed herein.

Figure 15B is a plot of stress S (MPa) versus depth D (mm) based on the LinQuad fit of Figure 15A to the OR and D data points.

Figure 16A is an exemplary OR vs. D plot that includes discrete data points (circles) and fitted lines to the OR vs. D data points, where the fitted line was formed using the power spike method disclosed herein.

FIG. 16B is a plot of stress S (MPa) versus depth D (mm) based on the power spike fit of OR and D data points (“S vs. D Graph”) of FIG. 16A.

Figures 17A and 17B are plots of OR vs. D curves showing the LinQuad curve fit for the initial (raw) OR and D data points (Figure 17A) and the OR vs. D data with the symmetric components removed LinQuad curve fitting (Fig. 17B).

Figures 18A and 18B are plots of OR and D showing the use of reduced area fitting regions in calculating selected stress parameters, where Figure 18A shows the curves used to calculate depth of compression DOC at bending points BP1 and BP2 and FIG. 18B shows the reduced area fitting region between bending points BP1 and BP2 for calculating the central tension CT.

Figure 19A is a plot of OR vs. D, and Figure 19B is a corresponding plot of S vs. D, where the curve fitting was performed on the entire set of OR data.

Figure 19C is a graph of OR vs. D, and Figure 19D is a corresponding plot of S vs. D, where the curve fitting was performed on a reduced set of OR data excluding portions of the data near opposite endpoints.

Fig. 20 is similar to Fig. 3A and shows an embodiment of an EPCS subsystem in which the detector system includes an adjustable focusing lens, wherein the adjustability includes at least one of moving axially and changing focus.

21A and 21B are schematic illustrations of exemplary support members for use in forming a focusing lens assembly for an EPCS subsystem to provide means for adjusting the contrast of the captured mode spectrum.

Figures 22A and 22B are similar to Figure 3A and show an example of an enhanced EPCS subsystem employing a light guide assembly.

Figure 22C is a close-up schematic diagram of an exemplary configuration of an EPCS subsystem employing Kohler illumination with respect to the output end of the light guide and the entrance pupil of the EPCS detector system.

FIG. 23 is a schematic diagram of an exemplary embodiment of a remote light source of an EPCS subsystem.

FIG. 24A is a front view of a filter wheel employed in the optical filter device of the remote light source system of FIG. 23. FIG.

Figure 24B shows two exemplary sequentially filtered EPCS beams, where the top example is formed using four filter wavelengths and the bottom example is formed using two filter wavelengths, as formed using the remote light source of Figure 23 .

Figures 25A-25C illustrate exemplary configurations of EPCS detector systems for augmenting EPCS subsystems.

Figure 26 is similar to Figure 4A and shows an example of an enhanced LSP subsystem.

FIG. 27A is a schematic diagram of an exemplary power monitoring system that may be implemented in the enhanced LSP subsystem of FIG. 26 .

Fig. 27B is a graph of (normalized) optical power OP versus polarization angle (degrees) for the transmitted and reflected portions of the beam of the power monitoring system of Fig. 27A.

Figure 28 is a graph of central tension CT (MPa) versus lens position LP (mm) (relative to a reference position) for an axially movable focusing lens showing the variation of CT with lens position and thus showing the effect on focused The LSP beam provides the importance of proper focus.

Figure 29 is similar to Figure 1 IB and shows the measured parameters of the LSP detector system relative to the CS substrate used to perform the calibration process.

Figure 30A is a graph of intensity I(p) versus pixel position p(x) along the LSP beam in the x direction for selected depths in a CS substrate and shows a sloped Gaussian fit to the measured intensities For an example of , this sloped Gaussian fit was used to estimate the center of the LSP beam, as indicated by the large black dot at the peak of the fitted curve (solid line).

Figure 30B is the pixel location p(x) and p(y) of the peak center as determined by the method associated with Figure 30A.

Figure 30C is a schematic diagram similar to Figure 10C showing the LSP image (intensity profile) with two overlapping fitted lines (FL1 and FL2) extending through the center of the two line image segments, two of which The intersection of the combined lines indicates the center point of the LSP image.

Figure 30D is a graph of LSP image intensity I(p) versus pixel position p along fitted line FL2 and near entry point EP, and is shown with maximum intensity _IMAX , _minimum intensity IMIN, and half-maximum intensity I An exemplary edge intensity profile of _1/2 , the half-maximum intensity I _1/2 resides midway between I _MAX and I _MIN and defines the location (pixel location) of the entry point ENP, which is approximately at pixel 32 in the exemplary graph .

Domestic deposit information (please note in order of depositor, date, and number) none Overseas storage information (please note in order of storage country, institution, date, and number) none

10: CS substrate

11: Subject

12: Top surface

14: Bottom surface

16: side

18:NSWG

Claims (11)

An Evanescent Coupling Spectroscopy (EPCS) system [100] for characterizing stress in a chemically enhanced (CS) substrate [10] having a surface [12] and a near-surface waveguide [18], the EPCS system [100] consists of: a) an EPCS light source system [110], the EPCS light source system [110] comprising: iv) an EPCS light source [112] emitting a multi-wavelength EPCS light beam [116]; v) an optical filter assembly [500] configured to sequentially filter the multi-wavelength EPCS beam to form a series of filtered EPCS beams having different wavelengths; vi) a light guide assembly [140] which transmits the series of filtered EPCS beams as guide light [116G] to a focusing optical system [121] which is passed through configured to receive the transmitted filtered EPCS beams and thereby form a series of filtered and focused EPCS beams [116F] b) an EPCS coupling beam [42A] forming an EPCS coupling surface [45A] with the surface of the CS substrate and receiving the series of filtered and focused EPCS beams [116F] and It is coupled into and out of the near-surface waveguide at the EPCS coupling surface to form a series of filtered and reflected EPCS beams [116R], the series of filtered and reflected EPCS beams [116R ] comprise the mode spectrum [160] of the near-surface waveguide for the corresponding filtered and reflected EPCS beam, respectively; and c) an EPCS detector system [140], the EPCS detector system [140] comprising: i) a switchable polarization filter [148S] operatively connected to a polarization controller [149] to sequentially perform transverse magnetic (TM) and Transverse Electric (TE) polarization filtering to form TM and TE filtered and reflected EPCS beams [116R] comprising the near TM mode spectra [161TM] and TE mode spectra [162TE] of surface waveguides; and ii) an EPCS digital detector [150] configured to sequentially detect the series of TM and TE filtered and reflected EPCS beams [116R] to sequentially capture TM and TE images of the corresponding TM and TE mode spectra of the near-surface waveguide at different filter wavelengths. A hybrid system [20] for characterizing stress in a chemically strengthened (CS) substrate [10] having a top surface [12] and a near-surface waveguide [18], the hybrid system [ 20] contains: The EPCS system [100] as described in Claim 1; A scattered light polarimetry (LSP) subsystem [200], the LSP subsystem [200] comprising an LSP light source system [210], an optical compensator [230] and an LSP detector system [240], the the LSP detector system [240] is in optical communication with the optical compensator via an LSP coupling plate [42B] having an LSP coupling surface [45B]; a coupling assembly [40], the coupling assembly [40] comprising a support frame [48] configured to operably support the EPCS coupling support frame [48] [42A] and the LSP coupling surface [42B] such that the EPCS coupling surface [45A] and the LSP coupling surface [45B] reside substantially in a common plane; and a support plenum [70] having a surface [71] and a measurement hole [72] configured to support the CS substrate on the measurement at a measurement plane [MP] at the hole, and the coupling assembly [40] is operably supported at the measurement hole such that the EPCS coupling surface and the LSP coupling surface substantially reside at the measurement plane. An Evanescent Coupling Spectroscopy (EPCS) system [100] for characterizing stress in a chemically enhanced (CS) substrate [10] having a surface [12] and a near-surface waveguide [18], the EPCS system [100] consists of: a) an EPCS light source system [110], the EPCS light source system [110] comprising: iv) an EPCS light source [112] emitting a multi-wavelength EPCS light beam [116]; v) an optical filter assembly [500] configured to sequentially filter the multi-wavelength EPCS beam to form a series of filtered EPCS beams having different filter wavelengths ; vi) a light guide assembly [140] configured to deliver the series of filtered EPCS light beams as guide light [116G] to a focusing optical system [121], the focusing optical system [121] configured to receive the transmitted filtered EPCS beams and thereby form a series of filtered and focused EPCS beams [116F]; b) an EPCS coupling interface [42A] which forms an EPCS coupling surface [45A] with the surface of the CS substrate and receives the focused sequentially filtered EPCS beam and transmits it at the coupled out of the near-surface waveguide at the EPCS coupling surface to form a reflected and sequentially filtered EPCS beam [116R] comprising the near-surface waveguide for at least the first at least first and second mode spectra [160] of the first and second filter wavelengths; and c) an EPCS detector system [140], the EPCS detector system [140] comprising: i) at least one switchable polarizing filter [148S] configured to sequentially perform Transverse Magnetic (TM) and Transverse Magnetic (TM) of the reflected and sequentially filtered EPCS beam electrical (TE) polarization filtering to form at least first and second TM- and TE-reflected and sequentially-filtered EPCS beams, the at least first and second TM- and TE-reflected and sequentially-filtered EPCS beams, respectively comprising first and second TM mode spectra [161TM] and TE mode spectra [161TE] of the near-surface waveguide at the at least first and second wavelengths; and ii) at least first and second EPCS digital detectors [150] configured to detect the at least first and second via TM respectively and TE reflected and sequentially filtered EPCS beams to capture respective at least first and second TM and TE images of the first and TM and TE mode spectra of the near-surface waveguide. A system [20] for characterizing stress in a chemically strengthened (CS) substrate [10] having a top surface [12] and a near-surface waveguide [18], the system [20] Include: The EPCS system [100] as described in Claim 3; A scattered light polarimetry (LSP) subsystem [200], the LSP subsystem [200] comprising an LSP light source system [210], an optical compensator [230] and an LSP detector system [240], the the LSP detector system [240] is in optical communication with the optical compensator via an LSP coupling plate [42B] having an LSP coupling surface [45B]; a coupling assembly [40], the coupling assembly [40] comprising a support frame [48] configured to operably support the EPCS coupling support frame [48] and the LSP coupling surface such that the EPCS coupling surface and the LSP coupling surface substantially reside in a common plane; and a support plenum [70] having a surface [71] and a measurement hole [72] configured to support the CS substrate on the measurement a measurement plane [MP] at the aperture, and the coupling assembly is operably supported at the measurement aperture such that the EPCS coupling surface and the LSP coupling surface substantially reside at the measurement plane. An Evanescent Coupling Spectroscopy (EPCS) system [100] for characterizing stress in a chemically enhanced (CS) substrate [10] having a surface [12] and a near-surface waveguide [18], the EPCS system [100] consists of: a) an EPCS light source system [110], the EPCS light source system [110] comprising: i) an EPCS light source [112] emitting a multi-wavelength EPCS light beam [116] comprising a plurality of wavelengths; ii) a light guide assembly [140] configured to deliver the multi-wavelength EPCS light beam from the EPCS light source to a focusing optics system [121] via configured to receive the multi-wavelength EPCS beam and form a focused multi-wavelength EPCS beam [116F]; b) an EPCS coupling beam [42A] that forms an EPCS coupling surface [45A] with the surface of the CS substrate and receives the multi-wavelength EPCS beam and couples it at the EPCS coupling surface coupling into and out of the near-surface waveguide to form a reflected multi-wavelength EPCS beam [116R] comprising the near-surface waveguide for the multi-wavelength EPCS beam the mode spectra[160] corresponding to multiple wavelengths; and c) an EPCS detector system [140], the EPCS detector system [140] comprising: i) a switchable polarization filter [148S] operatively positioned to receive the reflected multi-wavelength EPCS beam and in turn form a transverse magnetically polarized (TM) multi-wavelength EPCS beam and a transverse electric polarized (TE) multi-wavelength EPCS beam; ii) an optical filter assembly [500] operatively positioned to rely on the TM and the TE multi-wavelength EPCS beam at two or more filter wavelengths sequentially filtered to form two or more sequentially filtered TM and TE EPCS beams, the two or more sequentially filtered TM and TE EPCS beams respectively comprising the two or more filtered TM and TE mode spectrum of the wavelength of the device; iii) an EPCS digital detector [150] configured to sequentially detect the sequentially filtered TM and TE EPCS beams to sequentially capture the near surface waveguide at TM and TE images of the corresponding TM and TE mode spectra at the two or more filter wavelengths. A system [20] for characterizing stress in a chemically strengthened (CS) substrate [10] having a top surface [12] and a near-surface waveguide [18], the system [20] Include: The EPCS system [100] as described in Claim 5; A scattered light polarimetry (LSP) subsystem [200], the LSP subsystem [200] comprising an LSP light source system [210], an optical compensator [230] and an LSP detector system [240], the The LSP detector system [240] is in optical communication with the optical compensator via an LSP coupling plate [42B] having an LSP coupling surface [45B]; and a coupling assembly [40], the coupling assembly [40] comprising a support frame [48] configured to operably support the EPCS coupling support frame [48] and the LSP coupling surface such that the EPCS coupling surface and the LSP coupling surface substantially reside in a common plane; and a support plenum [70] having a surface [71] and a measurement hole [72] configured to support the CS substrate on the measurement a measurement plane [MP] at the aperture, and the coupling assembly is operably supported at the measurement aperture such that the EPCS coupling surface and the LSP coupling surface substantially reside at the measurement plane. A method of performing evanescent C-coupled spectroscopy to characterize stress in a chemically amplified (CS) substrate [10] having a surface [12] and a near-surface waveguide [18], the method Include: a) forming a multi-wavelength EPCS beam with multiple wavelengths [116]; b) sequentially filtering the EPCS multi-wavelength beam to form a series of filtered EPCS beams, the series of filtered EPCS beams each having a different one of the plurality of wavelengths; c) passing the series of EPCS filtered beams through a light guide [130] to a focusing optics system [121] to form a series of focused EPCS filtered beams [116F]; d) directing the series of focused filtered EPCS beams to an EPCS coupling surface [42A] which forms an EPCS coupling surface [45A] with the surface of the CS substrate and receives the and coupling a series of filtered EPCS beams into and out of the near-surface waveguide at the EPCS coupling surface to form a series of reflected and filtered EPCS beams [116R], the series of reflected and The filtered EPCS beams [116R] each comprise a mode spectrum [160] of the near-surface waveguide at one of the plurality of wavelengths; e) sequentially polarizing each of the reflected and filtered EPCS beams to form a transverse magnetic (TM) filtered and reflected EPCS beam and a transverse magnetic (TM) filtered EPCS beam for each reflected and filtered EPCS beam Electrically (TE) filtered and reflected EPCS beams; and f) sequentially digitally detecting the TM-filtered and reflected EPCS beam and the TE-filtered and reflected EPCS beam to sequentially capture the corresponding TM and TE modes of the near-surface waveguide for the different multiple wavelengths Spectrum TM and TE images. A light scattering polarimetry system [200] for characterizing stress in a chemically amplified (CS) substrate [10] having a body [11], a surface [12] and a formed on The near-surface waveguide [18] within the body, the light scattering polarimetry system [200] comprising: a) an LSP light source system [210], the LSP light source system [210] comprising in sequence along a first system axis (A3): i) a laser diode [213] emitting an LSP beam [216] having a power of at least 1 microwatt at a wavelength of 405 nm as a center; ii) an optical shutter system [280] configured to periodically block the LSP beam; iii) a rotatable half-wave plate [234RH]; iv) a first fixed polarizer [234H]; v) a first focusing lens [220]; vi) a light diffuser [222]; vii) a second focusing lens [224]; b) an optical compensator [230] disposed downstream of the LPS light source and configured to impart a time-varying polarization to the LSP beam, the optical compensator comprising in sequence along the system axis: i) a polarizing beam splitter [232] configured to receive the LSP beam from the LSP light source and transmit a first portion of the LSP beam along the first system axis and along a spectrometer axis [AS] directing a second portion of the LSP beam; ii) a spectrometer [260] arranged along the spectrometer axis and configured to receive and spectroscopically process the second portion of the LSP light beam; iii) a second fixed polarizer [234H]; iv) a variable polarizer [234V] imparting the time-varying polarization to the LSP beam to form a time-varyingly polarized LSP beam; c) an axially movable focusing lens [236] disposed downstream of the optical compensator and configured to receive and focus the time-varyingly polarized LSP beam to form a focused Time-varying polarization of LSP beams; d) an LSP coupling interface [42B] that interfaces with the surface of the CS substrate to form an LSP coupling interface [INT2], wherein the focused time-varyingly polarized LSP beam is focused on the LSP coupling interface to generate scattered light from stress-inducing features within the body of the CS substrate [216S]; e) an LSP detector system [240] disposed downstream of the LSP coupling channel and configured to receive the scattered light, the LSP detector system comprising: i) an LSP digit detector [246]; and ii) a collection optics system [243] that collects the scattered light and directs it to the LSP digital detector to form an LSP image [248] at the digital detector. A system [20] for characterizing stress in a chemically strengthened (CS) substrate [10] having a top surface [12] and a near-surface waveguide [18], the system [20] Include: The LSP system [200] as described in claim 8; an evanescent EPCS coupled spectroscopy (EPCS) subsystem [100] comprising an EPCS light source in optical communication via an EPCS coupled EPCS [42A] having an EPCS coupling surface [45A] system [110] and an EPCS detector system [140]; a coupling assembly [40], the coupling assembly [40] comprising a support frame [48] configured to operably support the EPCS coupling support frame [48] and the LSP coupling surface such that the EPCS coupling surface and the LSP coupling surface substantially reside in a common plane; and a support plenum [70] having a surface [71] and a measurement hole [72] configured to support the CS substrate on the measurement at a measurement plane at the bore, and the coupling assembly is operably supported at the measurement bore such that the EPCS coupling surface and the LSP coupling surface substantially reside at the measurement plane. A method of performing light scattering polarimetry (LSP) to characterize stress in a chemically amplified (CS) substrate [10] having a bulk [11], a surface [12] and a near surface waveguide [18], the near-surface waveguide [18] forming stress-dependent features within the body, the method comprising the steps of: generating a light beam [216] from a laser diode [213] having an output power of at least 1 microwatt and a central wavelength of 405 nm; directing a first portion of the beam to a spectrometer [26] to measure a wavelength of the beam and an amount of power in the beam; imparting a time-varying polarization to a second portion of the light beam using a temperature-controlled liquid crystal variable retarder (LCVR) [234V] to form a time-varyingly polarized light beam; focusing the time-varyingly polarized light beam onto a coupling surface [45B] formed by a coupling electrode [42B] interfacing with the surface of the CS substrate to remove the stresses within the body of the CS substrate Correlated features form scattered light [116S]; and The scattered light is directed to a digital detector [246] where an LSP image is captured [248]. The method of claim 10, comprising at least one of the following steps: a) wherein the time-varyingly polarized beam follows a beam path through the body of the CS substrate, and is estimated by A beam center (CNTR) of the beam: i) performing a tilted Gaussian fit to the scattered light for selected depths along the beam path into the body of the CS substrate to define a first set of beam centers; and ii ) fitting a first line through the centers of the first set of beams to define a first fitted line; b) estimating a center point of the time-varyingly polarized beams is performed by passing through the second fitting a second line to the center of the set of beams to define a second fitted line; and identifying the center point at which the first fitted line and the second fitted line intersect; and c) along the one of the first fitted line and the second fitted line identifies an edge intensity profile of the LSP image, wherein edge intensity transitions from a maximum value I _MAX to a minimum value I _MIN representing a background intensity value; and A half maximum intensity value I _1/2 between the maximum intensity value I _MAX and the minimum intensity value I _MIN is determined and the entry point is defined at the half maximum intensity value I _1/2 .

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